Anosmia and dysgeusia associated with SARS-CoV-2 infection: an age-matched case-control study

Mechanisms of COVID-19-associated olfactory dysfunction

Olfactory dysfunction is one of the most common symptoms of COVID-19. In the first 2 years of the pandemic, it was frequently reported, although its incidence has significantly decreased with the emergence of the Omicron variant, which has since become the dominant viral strain. Nevertheless, many patients continue to suffer from persistent dysosmia and dysgeusia, making COVID-19-associated olfactory dysfunction an ongoing health concern. The proposed pathogenic mechanisms of COVID-19-associated olfactory dysfunction are complex and likely multifactorial. While evidence suggests that infection of sustentacular cells and associated mucosal inflammation may be the culprit of acute, transient smell loss, alterations in other components of the olfactory system (e.g., olfactory receptor neuron dysfunction, olfactory bulb injury and alterations in the olfactory cortex) may lead to persistent, long-term olfactory dysfunction. This review aims to provide a comprehensive summary of the epidemiology, clinical manifestations and current understanding of the pathogenic mechanisms of COVID-19-associated olfactory dysfunction.

Viral Pneumonia: From Influenza to COVID-19

Respiratory viruses are increasingly recognized as a cause of community-acquired pneumonia (CAP). The implementation of new diagnostic technologies has facilitated their identification, especially in vulnerable population such as immunocompromised and elderly patients and those with severe cases of pneumonia. In terms of severity and outcomes, viral pneumonia caused by influenza viruses appears similar to that caused by non-influenza viruses. Although several respiratory viruses may cause CAP, antiviral therapy is available only in cases of CAP caused by influenza virus or respiratory syncytial virus. Currently, evidence-based supportive care is key to managing severe viral pneumonia. We discuss the evidence surrounding epidemiology, diagnosis, management, treatment, and prevention of viral pneumonia.

Photobiomodulation in the Treatment of Dysgeusia in Patients with Long COVID: A Single-Blind, Randomized Controlled Trial

Objective: The aim of this study is to evaluate local and systemic photobiomodulation (PBM) in patients with COVID-19-related dysgeusia, with the expectation of improving taste dysfunction. Background: PBM has garnered attention as a potential therapy in long COVID, a condition characterized by many persistent symptoms following the acute phase of COVID-19. Among these symptoms, dysgeusia, or altered taste perception, can significantly affect patients' quality of life. Emerging research suggests that PBM may hold promise in ameliorating dysgeusia by modulating cellular processes and reducing inflammation. Further clinical studies and randomized controlled trials are essential to establish the efficacy and safety of PBM for the treatment of dysgeusia in long COVID, but initial evidence suggests that this noninvasive modality may offer a novel avenue for symptom management. Methods: Seventy patients experiencing dysgeusia were randomly assigned to receive active local and systemic PBM (n = 34) or simulated PBM (n = 36). Low-power laser (red wavelength) was used at 18 spots on the lateral borders of the tongue (3 J per spot), salivary glands (parotid, sublingual, and submandibular glands-3 J per spot), and over the carotid artery for 10 min (60 J). Alongside laser therapy, all patients in both groups received weekly olfactory therapy for up to 8 weeks. Results: Dysgeusia improved in both groups. At weeks 7 and 8, improvement scores were significantly higher in the PBM group than in the sham group (p = 0.048). Conclusions: Combined local and systemic PBM, as applied in this study, proved effective and could serve as a viable treatment option for alleviating dysgeusia in long-COVID patients. Clinical Trial Registration: RBR-2mfbkkk.

Evaluation of Olfactory Dysfunction Among COVID-19 Patients in Baghdad, Iraq

Background SARS‑CoV‑2 (COVID-19) causes olfactory dysfunction which is characterized by anosmia or hyposmia. Characterization of olfactory dysfunction has added value to the diagnosis and prognosis of the disease. Nevertheless, scarce information exists about COVID-19 patients suffering from olfactory dysfunction in Iraq. This study aimed to identify olfactory dysfunction (anosmia or hyposmia) in Iraqi COVID-19 patients and examine their response to smell exercise at Baghdad Medical City Complex, Baghdad, Iraq. Methodology This case series prospective study involving 300 patients (160 males and 140 females) with COVID-19 infection was conducted from June 1, 2020, to October 1, 2021. We recorded signs and symptoms of COVID-19 among patients by examining olfactory dysfunction, n-butanol olfaction test, and smell test exercise. Results Anosmia and hyposmia were found in 69.3% and 30.7% of the patients, respectively; of these, 65.7% were of sudden onset. The association between olfactory dysfunction and smoking was not significant. The most frequent signs and symptoms of COVID-19 were fatigue, fever, loss of taste, myalgia, headache, sore throat, cough, depressed appetite, dyspnea, nausea, abdominal pain, and diarrhea. The highest frequencies of occurrence of anosmia (30.7%) and hyposmia (13.3%) were in the age group of 31-40 years. The majority (47.7%) of patients with olfactory dysfunction recovered within one month of COVID-19 onset. The rest of the patients recovered within one month to 16 months. The most commonly encountered ear, nose, and throat symptoms were nasal obstruction, rhinorrhea, and facial/ear pain. The percentages of patients with anosmia and hyposmia recovering with smell exercise were significant at 64.7% and 25.3%, respectively. Conclusions The prognosis of olfactory dysfunction in COVID-19 patients was good as most cases recovered within a short period with concomitant smell exercise. Olfactory dysfunction in the majority of COVID-19 patients was self-limiting in young age groups, albeit in association with the non-severity of the disease. Being an important public health issue, examining olfactory dysfunction aspects should be considered in the diagnosis, prognosis, and treatment protocols of COVID-19 patients. In-depth exploration is needed to examine olfactory and gustatory dysfunction in patients suffering from severe COVID-19.

Neurological complications and effects of COVID-19: Symptoms and conceivable mechanisms

A novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first identified in December 2019 in Wuhan, China. The new coronavirus disease (COVID-19) was declared a global pandemic by the World Health Organization (WHO) in March 2020. SARS-CoV-2 can invade the nervous system aside from infecting the respiratory system as its primary target. The most common nervous system symptoms of COVID-19 are stated as headache, myalgia, fatigue, nausea, vomiting, sudden and unexplained anosmia, and ageusia. More severe conditions such as encephalomyelitis, acute myelitis, thromboembolic events, ischemic stroke, intracerebral hemorrhage, Guillain-Barré-syndrome, Bell's palsy, rhabdomyolysis, and even coma have also been reported. Cohort studies revealed that neurological findings are associated with higher morbidity and mortality. The neurological symptoms and manifestations caused by SARS-CoV-2 and COVID-19 are examined and summarized in this article.

Gut distress and intervention via communications of SARS-CoV-2 with mucosal exposome

Acute coronavirus disease 2019 (COVID-19) has been associated with prevalent gastrointestinal distress, characterized by fecal shedding of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA or persistent antigen presence in the gut. Using a meta-analysis, the present review addressed gastrointestinal symptoms, such as nausea, vomiting, abdominal pain, and diarrhea. Despite limited data on the gut-lung axis, viral transmission to the gut and its influence on gut mucosa and microbial community were found to be associated by means of various biochemical mechanisms. Notably, the prolonged presence of viral antigens and disrupted mucosal immunity may increase gut microbial and inflammatory risks, leading to acute pathological outcomes or post-acute COVID-19 symptoms. Patients with COVID-19 exhibit lower bacterial diversity and a higher relative abundance of opportunistic pathogens in their gut microbiota than healthy controls. Considering the dysbiotic changes during infection, remodeling or supplementation with beneficial microbial communities may counteract adverse outcomes in the gut and other organs in patients with COVID-19. Moreover, nutritional status, such as vitamin D deficiency, has been associated with disease severity in patients with COVID-19 via the regulation of the gut microbial community and host immunity. The nutritional and microbiological interventions improve the gut exposome including the host immunity, gut microbiota, and nutritional status, contributing to defense against acute or post-acute COVID-19 in the gut-lung axis.

Assessment of factors influencing the olfactory bulb volume in patients with post-viral olfactory dysfunction

PURPOSE

To investigate the factors influencing the volume of the olfactory bulb (OB) in patients with post-viral olfactory dysfunction (PVOD).

METHODS

We collected 92 olfactory bulb volumes from patients with PVOD who underwent a sinus computed tomographic and magnetic resonance imaging (MRI) scan of the head and collected clinical information including gender, age, disease course, minimal cross-sectional area, nasal airway resistance, and olfactory function. OB volume was measured in MRI and the scans were evaluated according to the Lund-Mackay (LM) scoring system.

RESULTS

Male patients with PVOD had a larger OB volume (β = 0.284, P < 0.05). OB volume was smaller in patients with a longer course of olfactory dysfunction (β = - 0.254, P < 0.05). According to the LM scoring system, patients with a higher anterior ethmoidal sinus score had smaller OB volume (β = - 0.476, P < 0.05).

CONCLUSIONS

The study revealed that gender, disease course, and the score of anterior ethmoidal sinusitis can affect the OB volume in patients with PVOD.

Olfactory disorders in COVID-19 patients as a prognostic factor: a systematic review

Background

The reduction, loss, or impaired sense of smell and taste is common in patients with COVID-19. We aimed to investigate olfactory disorders (ODs) in patients with COVID-19 as a prognostic factor.

Methods

In this systematic review and meta-analysis, studies that assessed ODs in patients with COVID-19 were included. International databases, including PubMed, Embase, MEDLINE, Web of Science, and Scopus, were searched up to 20 March 2021. The random-effects model was used to combine the results of studies. Results were reported with a 95% confidence interval.

Results

In this study, out of 724 references, ten studies had the inclusion criteria. The odds of death in patients with the OD were 69% lower than in those without the ODs (OR = 0.31, 95% CI: 0.14, 0.69), and OD increased the odds of positive polymerase chain reaction (PCR) test (OR = 13.34, 95% CI: 4.2, 42.37).

Conclusions

The findings of our study showed that OD had an inverse and significant relationship with death in COVID-19 patients, and the patients with OD seemed to have a lower risk of mortality.

Taste loss as a distinct symptom of COVID-19: a systematic review and meta-analysis

Chemosensory scientists have been skeptical that reports of COVID-19 taste loss are genuine, in part because before COVID-19 taste loss was rare and often confused with smell loss. Therefore, to establish the predicted prevalence rate of taste loss in COVID-19 patients, we conducted a systematic review and meta-analysis of 376 papers published in 2020-2021, with 235 meeting all inclusion criteria. Drawing on previous studies and guided by early meta-analyses, we explored how methodological differences (direct vs. self-report measures) may affect these estimates. We hypothesized that direct measures of taste are at least as sensitive as those obtained by self-report and that the preponderance of evidence confirms taste loss is a symptom of COVID-19. The meta-analysis showed that, among 138,015 COVID-19-positive patients, 36.62% reported taste dysfunction (95% confidence interval: 33.02%-40.39%), and the prevalence estimates were slightly but not significantly higher from studies using direct (n = 15) versus self-report (n = 220) methodologies (Q = 1.73, df = 1, P = 0.1889). Generally, males reported lower rates of taste loss than did females, and taste loss was highest among middle-aged adults. Thus, taste loss is likely a bona fide symptom of COVID-19, meriting further research into the most appropriate direct methods to measure it and its underlying mechanisms.

Clinical manifestations of COVID-19 versus other upper respiratory tract infections in pediatric patients

OBJECTIVES

To explore the differences between COVID-19 and upper respiratory tract infections (URTI) in the pediatric population, emphasizing smell and taste disturbances.

METHODS

A case-control study included 468 patients, 234 with COVID-19 (cases) and 234 with URTI (controls) at a tertiary hospital, Riyadh, Saudi Arabia, from 2020-2021. Patients with bacterial URTI, lower tract respiratory infections, and speech or developmental delays were excluded. Statistical analysis was carried out using Statistical Analysis System, 9.2 version. A p-value of ≤0.05 was considered significant.

RESULTS

The male-to-female ratio was almost equal, with a mean age of 9.90±2.34. Multivariable logistic regression analysis showed that a change in taste significantly increases the probability of COVID-19 by 21.98 times. On the other hand, sore throat (81.5%), dyspnea (63.5%), nasal obstruction (72.7%), and otalgia significantly (74.8%) decrease the likelihood of COVID-19.

CONCLUSION

Taste disturbances increase the probability of COVID-19 infections, whereas sore throat, dyspnea, nasal obstruction, and otalgia increase the likelihood of other URTIs. The described differences might aid physicians in their differential diagnosis and treatment during the pandemic.

Neurological and Head/Eyes/Ears/Nose/Throat Manifestations of COVID-19: A Systematic Review and Meta-Analysis

BACKGROUND/OBJECTIVE

Coronavirus disease 2019 (COVID-19) has been associated with various neurological and atypical head/eyes/ears/nose/throat (HEENT) manifestations. We sought to review the evidence for these manifestations.

METHODS

In this systematic review and meta-analysis, we compiled studies published until March 31, 2021 that examined non-respiratory HEENT, central, and peripheral nervous system presentations in COVID-19 patients. We included 477 studies for qualitative synthesis and 59 studies for meta-analyses.

RESULTS

Anosmia, ageusia, and conjunctivitis may precede typical upper/lower respiratory symptoms. Central nervous system (CNS) manifestations include stroke and encephalopathy, potentially with brainstem or cranial nerve involvement. MRI studies support CNS para-/postinfectious etiologies, but direct neuroinvasion seems very rare, with few cases detecting Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in the CNS. Peripheral nervous system (PNS) manifestations include muscle damage, Guillain-Barre syndrome (GBS), and its variants. There was moderate-to-high study heterogeneity and risk of bias. In random-effects meta-analyses, anosmia/ageusia was estimated to occur in 56% of COVID-19 patients (95% CI: 0.41-0.71, I2:99.9%), more commonly than in patients without COVID-19 (OR: 14.28, 95% CI: 8.39-24.29, I2: 49.0%). Neurological symptoms were estimated to occur in 36% of hospitalized patients (95% CI: 0.31-0.42, I2: 99.8%); ischemic stroke in 3% (95% CI: 0.03-0.04, I2: 99.2%), and GBS in 0.04% (0.033%-0.047%), more commonly than in patients without COVID-19 (OR[stroke]: 2.53, 95% CI: 1.16-5.50, I2: 76.4%; OR[GBS]: 3.43,1.15-10.25, I2: 89.1%).

CONCLUSIONS

Current evidence is mostly from retrospective cohorts or series, largely in hospitalized or critically ill patients, not representative of typical community-dwelling patients. There remains a paucity of systematically gathered prospective data on neurological manifestations. Nevertheless, these findings support a high index of suspicion to identify HEENT/neurological presentations in patients with known COVID-19, and to test for COVID-19 in patients with such presentations at risk of infection.

Chronic rhinosinusitis is associated with increased risk of COVID-19 hospitalization

OBJECTIVE

The rationale of the study was to examine the association between chronic rhinosinusitis (CRS) and COVID-19 hospitalization.

STUDY DESIGN

Retrospective cohort study.

SETTING

Cleveland Clinic hospital inpatient and outpatient.

METHODS

A retrospective chart review of patients that were tested for COVID-19 at Cleveland Clinic. The study took place between March 8, 2020 and May 15, 2020.

RESULTS

From a total of 23,282 Patients that underwent SARS-CoV-2 testing, 996 COVID-19 negative and 998 COVID-19 positive patients were included in the analysis. COVID-19 positive patients with chronic rhinosinusitis (CRS) were at higher risk for hospitalization compared to patients without CRS (39.2% vs 25.7%, p = 0.0486). There was no significant difference between the two groups in relation to ICU admission, mechanical ventilation, and death, After adjustment for covariates, our multivariate analysis showed that patients with chronic rhinosinusitis (CRS) were approximately 3.46 (OR = 3.19, 95% CI (1.12-10.68)) times more likely to be hospitalized compared to patients that have no CRS.

CONCLUSION

Our results demonstrated that patients with chronic rhinosinusitis are associated with higher risk of COVID-19 hospitalization, albeit no increased risk of mortality.

Prevalence of the Clinical Symptoms and PCR Test Results on Patients With COVID-19 in South of Tehran

Background:

The first human case of COVID-19 was reported on 19 February 2020 in Iran, since then the number of infected cases has dramatically increased to about 1.800 million and about 62 000 deaths, also elderly people have accounted for the largest frequency of mortality.

Objective:

This study aims to evaluate the prevalence of Covid-19 RT-PCR positive among Iranian patients and to evaluate the most important clinical symptoms of identified patients based on age, gender, and their background diseases to be used as an aid for early diagnosis.

Methods:

During 9 months, swab samples of 11 034 patients’ nasopharynx and oropharynx secretions were obtained and were referred to the laboratory for Covid-19 RT-PCR test. In addition, the history of signs and symptoms from patients was recorded.

Results:

In total, 11 034 Covid-19 RT-PCR tests that performed, 3358 samples had positive results (30.4%). Headache was the most commonly reported, which was found in 42.5% of our cases. Fever was the second most common symptom among the patients studied, with a prevalence rate of 36.2%.

Conclusion:

In this study, almost 30% of symptomatic patients had positive Covid-19 RT-PCR test results. Headache was the most common symptom; also diarrhea and nausea were the least common symptoms among patients under this study.

Postmortem Assessment of Olfactory Tissue Degeneration and Microvasculopathy in Patients With COVID-19

Importance

Loss of smell is an early and common presentation of COVID-19 infection. Although it has been speculated that viral infection of olfactory neurons may be the culprit, it is unclear whether viral infection causes injuries in the olfactory bulb region.

Objective

To characterize the olfactory pathology associated with COVID-19 infection in a postmortem study.

Design, Setting, and Participants

This multicenter postmortem cohort study was conducted from April 7, 2020, to September 11, 2021. Deceased patients with COVID-19 and control individuals were included in the cohort. One infant with congenital anomalies was excluded. Olfactory bulb and tract tissue was collected from deceased patients with COVID-19 and appropriate controls. Histopathology, electron microscopy, droplet digital polymerase chain reaction, and immunofluorescence/immunohistochemistry studies were performed. Data analysis was conducted from February 7 to October 19, 2021.

Main Outcomes and Measures

(1) Severity of degeneration, (2) losses of olfactory axons, and (3) severity of microvasculopathy in olfactory tissue.

Results

Olfactory tissue from 23 deceased patients with COVID-19 (median [IQR] age, 62 [49-69] years; 14 men [60.9%]) and 14 control individuals (median [IQR] age, 53.5 [33.25-65] years; 7 men [50%]) was included in the analysis. The mean (SD) axon pathology score (range, 1-3) was 1.921 (0.569) in patients with COVID-19 and 1.198 (0.208) in controls (P < .001), whereas axon density was 2.973 (0.963) × 104/mm2 in patients with COVID-19 and 3.867 (0.670) × 104/mm2 in controls (P = .002). Concomitant endothelial injury of the microvasculature was also noted in olfactory tissue. The mean (SD) microvasculopathy score (range, 1-3) was 1.907 (0.490) in patients with COVID-19 and 1.405 (0.233) in control individuals (P < .001). Both the axon and microvascular pathology was worse in patients with COVID-19 with smell alterations than those with intact smell (mean [SD] axon pathology score, 2.260 [0.457] vs 1.63 [0.426]; P = .002; mean [SD] microvasculopathy score, 2.154 [0.528] vs 1.694 [0.329]; P = .02) but was not associated with clinical severity, timing of infection, or presence of virus.

Conclusions and Relevance

This study found that COVID-19 infection is associated with axon injuries and microvasculopathy in olfactory tissue. The striking axonal pathology in some cases indicates that olfactory dysfunction in COVID-19 infection may be severe and permanent.

Signs and symptoms to determine if a patient presenting in primary care or hospital outpatient settings has COVID-19

BACKGROUND

COVID-19 illness is highly variable, ranging from infection with no symptoms through to pneumonia and life-threatening consequences. Symptoms such as fever, cough, or loss of sense of smell (anosmia) or taste (ageusia), can help flag early on if the disease is present. Such information could be used either to rule out COVID-19 disease, or to identify people who need to go for COVID-19 diagnostic tests. This is the second update of this review, which was first published in 2020.

OBJECTIVES

To assess the diagnostic accuracy of signs and symptoms to determine if a person presenting in primary care or to hospital outpatient settings, such as the emergency department or dedicated COVID-19 clinics, has COVID-19.

SEARCH METHODS

We undertook electronic searches up to 10 June 2021 in the University of Bern living search database. In addition, we checked repositories of COVID-19 publications. We used artificial intelligence text analysis to conduct an initial classification of documents. We did not apply any language restrictions.

SELECTION CRITERIA

Studies were eligible if they included people with clinically suspected COVID-19, or recruited known cases with COVID-19 and also controls without COVID-19 from a single-gate cohort. Studies were eligible when they recruited people presenting to primary care or hospital outpatient settings. Studies that included people who contracted SARS-CoV-2 infection while admitted to hospital were not eligible. The minimum eligible sample size of studies was 10 participants. All signs and symptoms were eligible for this review, including individual signs and symptoms or combinations. We accepted a range of reference standards.

DATA COLLECTION AND ANALYSIS

Pairs of review authors independently selected all studies, at both title and abstract, and full-text stage. They resolved any disagreements by discussion with a third review author. Two review authors independently extracted data and assessed risk of bias using the QUADAS-2 checklist, and resolved disagreements by discussion with a third review author. Analyses were restricted to prospective studies only. We presented sensitivity and specificity in paired forest plots, in receiver operating characteristic (ROC) space and in dumbbell plots. We estimated summary parameters using a bivariate random-effects meta-analysis whenever five or more primary prospective studies were available, and whenever heterogeneity across studies was deemed acceptable.

MAIN RESULTS

We identified 90 studies; for this update we focused on the results of 42 prospective studies with 52,608 participants. Prevalence of COVID-19 disease varied from 3.7% to 60.6% with a median of 27.4%. Thirty-five studies were set in emergency departments or outpatient test centres (46,878 participants), three in primary care settings (1230 participants), two in a mixed population of in- and outpatients in a paediatric hospital setting (493 participants), and two overlapping studies in nursing homes (4007 participants). The studies did not clearly distinguish mild COVID-19 disease from COVID-19 pneumonia, so we present the results for both conditions together. Twelve studies had a high risk of bias for selection of participants because they used a high level of preselection to decide whether reverse transcription polymerase chain reaction (RT-PCR) testing was needed, or because they enrolled a non-consecutive sample, or because they excluded individuals while they were part of the study base. We rated 36 of the 42 studies as high risk of bias for the index tests because there was little or no detail on how, by whom and when, the symptoms were measured. For most studies, eligibility for testing was dependent on the local case definition and testing criteria that were in effect at the time of the study, meaning most people who were included in studies had already been referred to health services based on the symptoms that we are evaluating in this review. The applicability of the results of this review iteration improved in comparison with the previous reviews. This version has more studies of people presenting to ambulatory settings, which is where the majority of assessments for COVID-19 take place. Only three studies presented any data on children separately, and only one focused specifically on older adults. We found data on 96 symptoms or combinations of signs and symptoms. Evidence on individual signs as diagnostic tests was rarely reported, so this review reports mainly on the diagnostic value of symptoms. Results were highly variable across studies. Most had very low sensitivity and high specificity. RT-PCR was the most often used reference standard (40/42 studies). Only cough (11 studies) had a summary sensitivity above 50% (62.4%, 95% CI 50.6% to 72.9%)); its specificity was low (45.4%, 95% CI 33.5% to 57.9%)). Presence of fever had a sensitivity of 37.6% (95% CI 23.4% to 54.3%) and a specificity of 75.2% (95% CI 56.3% to 87.8%). The summary positive likelihood ratio of cough was 1.14 (95% CI 1.04 to 1.25) and that of fever 1.52 (95% CI 1.10 to 2.10). Sore throat had a summary positive likelihood ratio of 0.814 (95% CI 0.714 to 0.929), which means that its presence increases the probability of having an infectious disease other than COVID-19. Dyspnoea (12 studies) and fatigue (8 studies) had a sensitivity of 23.3% (95% CI 16.4% to 31.9%) and 40.2% (95% CI 19.4% to 65.1%) respectively. Their specificity was 75.7% (95% CI 65.2% to 83.9%) and 73.6% (95% CI 48.4% to 89.3%). The summary positive likelihood ratio of dyspnoea was 0.96 (95% CI 0.83 to 1.11) and that of fatigue 1.52 (95% CI 1.21 to 1.91), which means that the presence of fatigue slightly increases the probability of having COVID-19. Anosmia alone (7 studies), ageusia alone (5 studies), and anosmia or ageusia (6 studies) had summary sensitivities below 50% but summary specificities over 90%. Anosmia had a summary sensitivity of 26.4% (95% CI 13.8% to 44.6%) and a specificity of 94.2% (95% CI 90.6% to 96.5%). Ageusia had a summary sensitivity of 23.2% (95% CI 10.6% to 43.3%) and a specificity of 92.6% (95% CI 83.1% to 97.0%). Anosmia or ageusia had a summary sensitivity of 39.2% (95% CI 26.5% to 53.6%) and a specificity of 92.1% (95% CI 84.5% to 96.2%). The summary positive likelihood ratios of anosmia alone and anosmia or ageusia were 4.55 (95% CI 3.46 to 5.97) and 4.99 (95% CI 3.22 to 7.75) respectively, which is just below our arbitrary definition of a 'red flag', that is, a positive likelihood ratio of at least 5. The summary positive likelihood ratio of ageusia alone was 3.14 (95% CI 1.79 to 5.51). Twenty-four studies assessed combinations of different signs and symptoms, mostly combining olfactory symptoms. By combining symptoms with other information such as contact or travel history, age, gender, and a local recent case detection rate, some multivariable prediction scores reached a sensitivity as high as 90%.

AUTHORS' CONCLUSIONS

Most individual symptoms included in this review have poor diagnostic accuracy. Neither absence nor presence of symptoms are accurate enough to rule in or rule out the disease. The presence of anosmia or ageusia may be useful as a red flag for the presence of COVID-19. The presence of cough also supports further testing. There is currently no evidence to support further testing with PCR in any individuals presenting only with upper respiratory symptoms such as sore throat, coryza or rhinorrhoea. Combinations of symptoms with other readily available information such as contact or travel history, or the local recent case detection rate may prove more useful and should be further investigated in an unselected population presenting to primary care or hospital outpatient settings. The diagnostic accuracy of symptoms for COVID-19 is moderate to low and any testing strategy using symptoms as selection mechanism will result in both large numbers of missed cases and large numbers of people requiring testing. Which one of these is minimised, is determined by the goal of COVID-19 testing strategies, that is, controlling the epidemic by isolating every possible case versus identifying those with clinically important disease so that they can be monitored or treated to optimise their prognosis. The former will require a testing strategy that uses very few symptoms as entry criterion for testing, the latter could focus on more specific symptoms such as fever and anosmia.

Intranasal delivery of SARS-CoV-2 spike protein is sufficient to cause olfactory damage, inflammation and olfactory dysfunction in zebrafish

Anosmia, loss of smell, is a prevalent symptom of SARS-CoV-2 infection. Anosmia may be explained by several mechanisms driven by infection of non-neuronal cells and damage in the nasal epithelium rather than direct infection of olfactory sensory neurons (OSNs). Previously, we showed that viral proteins are sufficient to cause neuroimmune responses in the teleost olfactory organ (OO). We hypothesize that SARS-CoV-2 spike (S) protein is sufficient to cause olfactory damage and olfactory dysfunction. Using an adult zebrafish model, we report that intranasally delivered SARS-CoV-2 S RBD mostly binds to the non-sensory epithelium of the olfactory organ and causes severe olfactory histopathology characterized by loss of cilia, hemorrhages and edema. Electrophysiological recordings reveal impaired olfactory function to both food and bile odorants in animals treated intranasally with SARS-CoV-2 S RBD. However, no loss of behavioral preference for food was detected in SARS-CoV-2 S RBD treated fish. Single cell RNA-Seq of the adult zebrafish olfactory organ indicated widespread loss of olfactory receptor expression and inflammatory responses in sustentacular, endothelial, and myeloid cell clusters along with reduced numbers of T_regs. Combined, our results demonstrate that intranasal SARS-CoV-2 S RBD is sufficient to cause structural and functional damage to the zebrafish olfactory system. These findings may have implications for intranasally delivered vaccines against SARS-CoV-2.

Symptoms associated with a COVID-19 infection among a non-hospitalized cohort in Vienna

Background

Most clinical studies report the symptoms experienced by those infected with coronavirus disease 2019 (COVID-19) via patients already hospitalized. Here we analyzed the symptoms experienced outside of a hospital setting.

Methods

The Vienna Social Fund (FSW; Vienna, Austria), the Public Health Services of the City of Vienna (MA15) and the private company Symptoma collaborated to implement Vienna’s official online COVID-19 symptom checker. Users answered 12 yes/no questions about symptoms to assess their risk for COVID-19. They could also specify their age and sex, and whether they had contact with someone who tested positive for COVID-19. Depending on the assessed risk of COVID-19 positivity, a SARS-CoV‑2 nucleic acid amplification test (NAAT) was performed. In this publication, we analyzed which factors (symptoms, sex or age) are associated with COVID-19 positivity. We also trained a classifier to correctly predict COVID-19 positivity from the collected data.

Results

Between 2 November 2020 and 18 November 2021, 9133 people experiencing COVID-19-like symptoms were assessed as high risk by the chatbot and were subsequently tested by a NAAT. Symptoms significantly associated with a positive COVID-19 test were malaise, fatigue, headache, cough, fever, dysgeusia and hyposmia. Our classifier could successfully predict COVID-19 positivity with an area under the curve (AUC) of 0.74.

Conclusion

This study provides reliable COVID-19 symptom statistics based on the general population verified by NAATs.

Supplementary Information

The online version of this article (10.1007/s00508-022-02028-9) contains supplementary material, which is available to authorized users.

Performance of formal smell testing and symptom screening for identifying SARS-CoV-2 infection

Background

Altered sense of smell is a commonly reported COVID-19 symptom. The performance of smell testing to identify SARS-CoV-2 infection status is unknown. We measured the ability of formal smell testing to identify SARS-CoV-2 infection and compared its performance with symptom screening.

Methods

A convenience sample of emergency department patients with COVID-19 symptom screening participated in smell testing using an eight odor Pocket Smell Test (PST). Participants received a SARS-CoV-2 viral PCR test after smell testing and completed a health conditions survey. Descriptive analysis and receiver operating characteristic (ROC) curve models compared the accuracy of smell testing versus symptom screening in identifying SARS-CoV-2 infection.

Results

Two hundred and ninety-five patients completed smell testing and 87 (29.5%) had a positive SARS-CoV-2 PCR test. Twenty-eight of the SARS-CoV-2 positive patients (32.2%) and 49 of the SARS-CoV-2 negative patients (23.6%) reported at least one of seven screening symptoms (OR = 1.54, P = 0.13). SARS-CoV-2 positive patients were more likely to have hyposmia (≤5 correctly identified odors) than SARS-CoV-2 negative patients (56.1% vs. 19.3%, OR = 5.36, P<0.001). Hyposmia was 52.9% (95% CI 41.9%-63.7%) sensitive and 82.7% (95% CI 76.9%-87.6%) specific for SARS-CoV-2 infection. Presence of ≥1 screening symptom was 32.2% (95% CI 22.6%-43.1%) sensitive and 76.4% (70.1%-82.0%) specific for SARS-CoV-2 infection. The ROC curve for smell testing had an area under the curve (AUC) of 0.74 (95% CI 0.67–0.80). The ROC curve for symptom screening had lower discriminatory accuracy for SARS-CoV-2 infection (AUC = 0.55, 95% CI 0.49–0.61, P<0.001) than the smell testing ROC curve.

Conclusion

Smell testing was superior to symptom screening for identifying SARS-CoV-2 infection in our study.

How common are taste and smell abnormalities in COVID-19? A systematic review and meta-analysis

OBJECTIVE

Olfactory and gustatory dysfunction (OGD) are important early clinical symptoms of COVID-19. We aim to calculate the pooled prevalence of these symptoms and discuss the likely implications on clinical practice such as their use as screening tools and potential prognosis indicators.

METHODS

Using a combination of keywords and medical subject headings, we searched for observational studies in the following five databases: Medline/PubMed, Scopus, Cochrane Library, Web of Science, and Google Scholar. Two authors independently screened and selected the final articles according to the inclusion criteria. Two investigators independently assessed the risk of bias in individual studies using the Newcastle-Ottawa Scale. Heterogeneity and publication bias were also assessed. The reported outcome of the pooled analysis was the prevalence of OGD calculated using a random-effect model. Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed to report results.

RESULTS

Seventeen studies with a total sample size of 4149 were included in this meta-analysis. Out of these, 2106 and 2676 patients reported some degree of olfactory and/or gustatory dysfunction with COVID-19, respectively. The reported outcomes were in terms of pooled prevalence, with gustatory dysfunction being 57.33% and olfactory dysfunction being 59.69%, a significantly high occurrence.

CONCLUSION

There is a high occurrence of smell and taste impairment in COVID-19. Given the lack of objective testing for detecting OGD in most studies, the high prevalence found is likely to be an underestimation of the true prevalence. This implies that physicians must use them as reliable early indicators of COVID-19 and employ them before using expensive tests.

Gustatory and Saliva Secretory Dysfunctions in COVID-19 Patients with Zinc Deficiency

Given the ever-progressing studies on coronavirus disease 2019 (COVID-19), it is critical to update our knowledge about COVID-19 symptomatology and pathophysiology. In the present narrative review, oral symptoms were overviewed using the latest data and their pathogenesis was hypothetically speculated. PubMed, LitCovid, ProQuest, and Google Scholar were searched for relevant studies from 1 April 2021 with a cutoff date of 31 January 2022. The literature search indicated that gustatory dysfunction and saliva secretory dysfunction are prevalent in COVID-19 patients and both dysfunctions persist after recovery from the disease, suggesting the pathogenic mechanism common to these cooccurring symptoms. COVID-19 patients are characterized by hypozincemia, in which zinc is possibly redistributed from blood to the liver at the expense of zinc in other tissues. If COVID-19 induces intracellular zinc deficiency, the activity of zinc-metalloenzyme carbonic anhydrase localized in taste buds and salivary glands may be influenced to adversely affect gustatory and saliva secretory functions. Zinc-binding metallothioneins and zinc transporters, which cooperatively control cellular zinc homeostasis, are expressed in oral tissues participating in taste and saliva secretion. Their expression dysregulation associated with COVID-19-induced zinc deficiency may have some effect on oral functions. Zinc supplementation is expected to improve oral symptoms in COVID-19 patients.

Severe Infections Due to Respiratory Viruses

Severe viral infections may result in severe illnesses capable of causing acute respiratory failure that could progress rapidly to acute respiratory distress syndrome (ARDS), related to worse outcomes, especially in individuals with a higher risk of infection, including the elderly and those with comorbidities such as asthma, diabetes mellitus and chronic respiratory or cardiovascular disease. In addition, in cases of severe viral pneumonia, co-infection with bacteria such as Streptococcus pneumoniae and Staphylococcus aureus is related to worse outcomes. Respiratory viruses like influenza, rhinovirus, parainfluenza, adenovirus, metapneumovirus, respiratory syncytial virus, and coronavirus have increasingly been detected. This trend has become more prevalent, especially in critically ill patients, due to the availability and implementation of molecular assays in clinical practice. Respiratory viruses have been diagnosed as a frequent cause of severe pneumonia, including cases of community-acquired pneumonia, hospital-acquired pneumonia, and ventilator-associated pneumonia. In this review, we will discuss the epidemiology, diagnosis, clinical characteristics, management, and prognosis of patients with severe infections due to respiratory viruses, with a focus on influenza viruses, non-influenza viruses, and coronaviruses.

Neurological Associations of SARS-CoV-2 Infection: A Systematic Review

BACKGROUND

The current ongoing COVID-19 pandemic has compelled us to scrutinize major outbreaks in the past two decades, Severe Acute Respiratory Syndrome (SARS), in 2002, and Middle East Respiratory Syndrome (MERS), in 2012. We aimed to assess the associated neurological manifestations with SARS CoV-2 infection.

METHODS

In this systematic review, a search was carried out by key-electronic databases, controlled vocabulary, and indexing of trials to evaluate the available pertinent studies which included both medical subject headings (MeSH) and advanced electronic databases comprising PubMed, Embase, Scopus, Cochrane Central Register of Controlled Trials (CENTRAL). Peer-reviewed studies published in English and Spanish were considered, which reported data on the neurological associations of individuals with suspected or laboratory-confirmed SARS-CoV-2 infection. Outcomes were nervous signs or symptoms, symptom severity, and diagnoses.

RESULTS

Our search identified 45 relevant studies, with 21 case reports, 3 case series, 9 observational studies, 1 retrospective study, 9 retrospective reviews, and 2 prospective reviews. This systematic review revealed that most commonly reported neuronal presentations involved headache, nausea, vomiting and muscular symptoms like fibromyalgia. Anosmia and ageusia, defects in clarity or sharpness of vision (error in visual acuity), and pain may occur in parallel. Notable afflictions in the form of anxiety, anger, confusion, post-traumatic stress symptoms, and post-intensive care syndrome were observed in individuals who were kept in quarantine and those with long-stay admissions in healthcare settings. SARS CoV-2 infection may result in cognitive impairment. Patients with more severe infection exhibited uncommon manifestations, such as acute cerebrovascular diseases (intracerebral haemorrhage, stroke), rhabdomyolysis, encephalopathy, and Guillain-Barré syndrome.

CONCLUSION

SARS-CoV-2 patients experience neuronal presentations varying with the progression of the infection. Healthcare professionals should be acquainted with the divergent neurological symptoms to curb misdiagnosis and limit long-term sequelae. Health-care planners and policymakers must prepare for this eventuality, while the ongoing studies increase our knowledge base on acute and chronic neurological associations of this pathogen.

Taste loss as a distinct symptom of COVID-19: a systematic review and meta-analysis

Chemosensory scientists have been skeptical that reports of COVID-19 taste loss are genuine, in part because before COVID-19 taste loss was rare and often confused with smell loss. Therefore, to establish the predicted prevalence rate of taste loss in COVID-19 patients, we conducted a systematic review and meta-analysis of 376 papers published in 2020-2021, with 241 meeting all inclusion criteria. Drawing on previous studies and guided by early meta-analyses, we explored how methodological differences (direct vs. self-report measures) may affect these estimates. We hypothesized that direct measures of taste are at least as sensitive as those obtained by self-report and that the preponderance of evidence confirms taste loss is a symptom of COVID-19. The meta-analysis showed that, among 138,897 COVID-19-positive patients, 39.2% reported taste dysfunction (95% confidence interval: 35.34%-43.12%), and the prevalence estimates were slightly but not significantly higher from studies using direct (n = 18) versus self-report (n = 223) methodologies (Q = 0.57, df = 1, P = 0.45). Generally, males reported lower rates of taste loss than did females, and taste loss was highest among middle-aged adults. Thus, taste loss is likely a bona fide symptom of COVID-19, meriting further research into the most appropriate direct methods to measure it and its underlying mechanisms.

Iranian Smell Diagnostic Test in Covid-19 Disease; Report of Covid-19 Center of North of Iran

Background

SARS-CoV-2 is a pandemic coronavirus that causes the COVID-19 syndrome. In the pandemic of COVID-19 many patients were affected to new onset olfactory dysfunction. Since there is a dearth of research studies regarding the standard smell test, the present study was conducted to fill this gap.

Methods

The present retrospective cohort study was conducted on 250 clients with or without diagnosis of Covid-19 disease who referred to Covid-19 centers of North of Iran. Two groups were matched for age and sex. Data were collected by examination, demographic and clinical information questionnaire and Iranian smell diagnostic test. The binary logistic regression to estimate the odds ratio value in SPSS version 23.0 was used.

Results

One-hundred cases (42.2%) had hyposmia and 20 cases (8.4%) were found to have anosmia. Type of covid-19 sign and symptom were statistically significant with olfactory dysfunction (41 cases, 31.8%), fever (28 cases, 21.7%), weakness and dyspnea (15 cases, 11.6%), (p=0.0001). The urban residency equal OR=6.42 (3.04-13.53) to rural residency for olfactory dysfunction (p=0.0001). Covid-19 patients' OR=61.25 (27.36-137.11) chance to be affected by the olfactory dysfunction in compare to control group (p=0.0001). Also, with increasing age, chance of olfactory dysfunction changed from OR=0.61(1.16-0.13) to OR=1.89 (0.82-4.33). Furthermore, female chance OR=1.21 (0.72-2.03) and employee patients was OR=2.29 (1.30-4.04) to olfactory dysfunction.

Conclusion

Alf of the patients were affected by olfactory dysfunction. Furthermore, Covid-19 patients, urban residency, lower age, female and employee were the prognostic factors for olfactory dysfunction. The standard olfactory tests such as IR-SIT is suggested for screening and detecting the clients probably affected by covid-19 especially in younger ages.

Covid-19: Signs and symptoms related to the feeding behavior

COVID-19 reached pandemic level in March 2020 and the number of confirmed cases continued to increase worldwide. The clinical course of the disease has not yet been fully characterized, and some specific symptoms related to smell, taste, and feeding behavior require further examination. The present study aimed to assess the presence of symptoms related to the feeding behavior occurred during and/or after COVID-19 in adults residing in Portugal and to link them to disease severity using a multivariate approach. Data were collected from May to September 2020, through a questionnaire answered online containing questions about general and specific symptoms before, during and after COVID-19. 362 participants were included: 201 were symptomatic, being 15 hospitalized and 186 non-hospitalized. Cluster analysis grouped the symptomatic non-hospitalized participants as mild and severe cases. For these patients, the most frequent symptoms related to the feeding process were smell disorders in 40% and 62%, taste disorders in 37% and 60%, and dry mouth, in 23% and 48% of the mild and severe cases, respectively. Dry mouth was significantly associated with difficulty to swallow, pain during swallow, choking when eating or drinking, and preference for mushy/pasty foods (p < 0.01; Chi-squared test). Among the severe cases, the incidence of coughing during the meal (31%), difficulty (19%) and pain during swallow (17%), preference for mushy/pasty foods (10%) and choking when eating or drinking (6%) were clinically relevant and may indicate the presence of swallowing disorders. This group also showed a higher frequency of general symptoms, such as fever, headache, abdominal pain, tiredness, diarrhea, nausea, and shortness of breath (p < 0.05; Chi-squared test). Smell disorders, taste disorders and dry mouth were the most frequent symptoms related to the feeding behavior for both mild and severe cases. Dry mouth was significantly associated with swallowing difficulties and future research should investigate it as a frequent symptom and as a predictive of the presence of eating and swallowing disorders in COVID-19 cases.

Exploring the Clinical Utility of Gustatory Dysfunction (GD) as a Triage Symptom Prior to Reverse Transcription Polymerase Chain Reaction (RT-PCR) in the Diagnosis of COVID-19: A Meta-Analysis and Systematic Review

BACKGROUND

The diagnosis of COVID-19 is made using reverse transcription polymerase chain reaction (RT-PCR) but its sensitivity varies from 20 to 100%. The presence of gustatory dysfunction (GD) in a patient with upper respiratory tract symptoms might increase the clinical suspicion of COVID-19.

AIMS

To perform a systematic review and meta-analysis to determine the pooled sensitivity, specificity, positive likelihood ratio (LR+), negative likelihood ratio (LR-) and diagnostic odds ratio (DOR) of using GD as a triage symptom prior to RT-PCR.

METHODS

PubMed and Embase were searched up to 20 June 2021. Studies published in English were included if they compared the frequency of GD in COVID-19 adult patients (proven by RT-PCR) to COVID-19 negative controls in case control or cross-sectional studies. The Newcastle-Ottawa scale was used to assess the methodological quality of the included studies.

RESULTS

21,272 COVID-19 patients and 52,298 COVID-19 negative patients were included across 44 studies from 21 countries. All studies were of moderate to high risk of bias. Patients with GD were more likely to test positive for COVID-19: DOR 6.39 (4.86-8.40), LR+ 3.84 (3.04-4.84), LR- 0.67 (0.64-0.70), pooled sensitivity 0.37 (0.29-0.47) and pooled specificity 0.92 (0.89-0.94). While history/questionnaire-based assessments were predictive of RT-PCR positivity (DOR 6.62 (4.95-8.85)), gustatory testing was not (DOR 3.53 (0.98-12.7)). There was significant heterogeneity among the 44 studies (I2 = 92%, p < 0.01).

CONCLUSIONS

GD is useful as a symptom to determine if a patient should undergo further testing, especially in resource-poor regions where COVID-19 testing is scarce. Patients with GD may be advised to quarantine while repeated testing is performed if the initial RT-PCR is negative.

FUNDING

None.

Self-reported olfactory and gustatory dysfunction and psychophysical testing in screening for Covid-19: A systematic review and meta-analysis

Background

A substantial proportion of coronavirus disease‐2019 (COVID‐19) patients demonstrate olfactory and gustatory dysfunction (OGD). Self‐reporting for OGD is widely used as a predictor of COVID‐19. Although psychophysical assessment is currently under investigation in this role, the sensitivity of these screening tests for COVID‐19 remains unclear. In this systematic review we assess the sensitivity of self‐reporting and psychophysical tests for OGD.

Methods

A systematic search was performed on PubMed, EMBASE, and ClinicalTrials.gov from inception until February 16, 2021. Studies of suspected COVID‐19 patients with reported smell or taste alterations were included. Data were pooled for meta‐analysis. Sensitivity, specificity, and diagnostic odds ratio (DOR) were reported in the outcomes.

Results

In the 50 included studies (42,902 patients), self‐reported olfactory dysfunction showed a sensitivity of 43.9% (95% confidence interval [CI], 37.8%‐50.2%), a specificity of 91.8% (95% CI, 89.0%‐93.9%), and a DOR of 8.74 (95% CI, 6.67‐11.46) for predicting COVID‐19 infection. Self‐reported gustatory dysfunction yielded a sensitivity of 44.9% (95% CI, 36.4%‐53.8%), a specificity of 91.5% (95% CI, 87.7%‐94.3%), and a DOR of 8.83 (95% CI, 6.48‐12.01). Olfactory psychophysical tests analysis revealed a sensitivity of 52.8% (95% CI, 25.5%‐78.6%), a specificity of 88.0% (95% CI, 53.7%‐97.9%), and a DOR of 8.18 (95% CI, 3.65‐18.36). One study used an identification test for gustatory sensations assessment.

Conclusion

Although demonstrating high specificity and DOR values, neither self‐reported OGD nor unvalidated and limited psychophysical tests were sufficiently sensitive in screening for COVID‐19. They were not suitable adjuncts in ruling out the disease.

Seroprevalence of anti-SARS-CoV-2 IgG at the first epidemic peak in French Guiana, July 2020

BACKGROUND

While Latin America has been heavily affected by the pandemic, only a few seroprevalence studies have been conducted there during the first epidemic wave in the first half of 2020.

METHODOLOGY/PRINCIPAL FINDINGS

A cross-sectional survey was performed between 15 July 2020 and 23 July 2020 among individuals who visited 4 medical laboratories or 5 health centers for routine screening or clinical management, with the exception of symptomatic suggestive cases of covid-19. Samples were screened for the presence of anti-SARS-CoV-2 IgG directed against domain S1 of the SARS-CoV-2 spike protein using the anti-SARS-CoV-2 enzyme-linked immunosorbent assay (ELISA) from Euroimmun.

CONCLUSIONS/SIGNIFICANCE

The overall seroprevalence was 15.4% [9.3%-24.4%] among 480 participants, ranging from 4.0% to 25.5% across the different municipalities. The seroprevalence did not differ according to gender (p = 0.19) or age (p = 0.51). Among SARS-CoV-2 positive individuals, we found that 24.6% [11.5%-45.2%] reported symptoms consistent with COVID-19. Our findings revealed high levels of infection across the territory but a low number of resulting deaths, which can be explained by French Guiana's young population structure.

Taste loss as a distinct symptom of COVID-19: A systematic review and meta-analysis

Chemosensory scientists have been skeptical that reports of COVID-19 taste loss are genuine, in part because before COVID-19, taste loss was rare and often confused with smell loss. Therefore, to establish the predicted prevalence rate of taste loss in COVID-19 patients, we conducted a systematic review and meta-analysis of 376 papers published in 2020-2021, with 241 meeting all inclusion criteria. Additionally, we explored how methodological differences (direct vs. self-report measures) may affect these estimates. We hypothesized that direct prevalence measures of taste loss would be the most valid because they avoid the taste/smell confusion of self-report. The meta-analysis showed that, among 138,897 COVID-19-positive patients, 39.2% reported taste dysfunction (95% CI: 35.34-43.12%), and the prevalence estimates were slightly but not significantly higher from studies using direct (n = 18) versus self-report (n = 223) methodologies (Q = 0.57, df = 1, p = 0.45). Generally, males reported lower rates of taste loss than did females and taste loss was highest in middle-aged groups. Thus, taste loss is a bona fide symptom COVID-19, meriting further research into the most appropriate direct methods to measure it and its underlying mechanisms.

Association between new-onset anosmia and positive SARS-CoV-2 tests among people accessing outpatient testing in Toronto, Ontario: a retrospective cross-sectional study

BACKGROUND

Reports have suggested that anosmia is strongly associated with SARS-CoV-2 infection, but patients were often asked about this symptom after their diagnosis. This study assessed associations between prospectively reported anosmia and other symptoms related to SARS-CoV-2 infection, and SARS-CoV-2 positivity in community testing centres in Toronto, Ontario.

METHODS

We conducted a retrospective cross-sectional study in which data were collected from 2 COVID-19 assessment centres affiliated with 2 hospitals in Toronto, Ontario, from Apr. 5 to Sept. 30, 2020. We included symptomatic profiles of all people who underwent a SARS-CoV-2 test at either clinic within the study period. We used generalized estimating equations to account for repeat visits and to assess associations between anosmia and other symptoms and SARS-CoV-2 positivity.

RESULTS

A total of 83 443 SARS-CoV-2 tests were conducted across the 2 sites for 72 692 participants during the study period. Of all tests, 1640 (2.0%) were positive; 837 (51.0%) of people who tested positive were asymptomatic. The adjusted odds ratio for the association between anosmia and test positivity was 5.29 (95% confidence interval [CI] 4.50-6.22), with sensitivity of 0.138 (95% CI 0.121-0.154), specificity of 0.980 (95% CI 0.979-0.981), a positive predictive value of 0.120 (95% CI 0.106-0.135) and a negative predictive value of 0.983 (95% CI 0.982-0.984).

INTERPRETATION

Anosmia had high specificity and a positive predictive value of 12% for SARS-CoV-2 infection in this community population with low prevalence of SARS-CoV-2 positivity. The presence of anosmia should increase clinical suspicion of SARS-CoV-2 infection, and our findings suggest that people presenting with this symptom should be tested.

Simple Disposable Odor Identification Tests for Predicting SARS-CoV-2 Positivity

Olfactory dysfunction (OD) is a common manifestation of COVID-19 and may be useful for screening. Survey-based olfactory evaluation tends to underestimate the prevalence of OD, while psychophysical olfactory testing during a pandemic has the disadvantage of being time consuming, expensive, and requiring standardized laboratory settings. We aimed to develop a quick, simple, affordable, and reliable test to objectively assess the prevalence and diagnostic accuracy of OD in COVID-19. The olfactory function of 64 COVID-19 inpatients and 34 controls was evaluated using a questionnaire and a simple disposable odor identification test (SDOIT) developed for this study. Four SDOIT models were assessed: 10-SDOIT, 9-SDOIT, 8-SDOIT, and 4-SDOIT, with 10, 9, 8 and 4 samples, respectively. We found a high frequency of self-reported OD in COVID-19 patients, with 32.8% and 42.2% reporting current and recent OD, respectively. Different SDOIT models revealed smell impairment in 54.7-64.1% of COVID-19 patients. The combination of either 10-SDOIT results and self-reported OD, or 8-SDOIT results and self-reported OD, were the best predictors of COVID-19, both with an AUC value of 0.87 (0.85 and 0.86 for the age-matched subjects). OD is a common symptom of COVID-19. A combination of self-reported smell deterioration and OD psychophysically evaluated using SDOIT appears to be a good predictor of COVID-19.

Olfactory dysfunction in SARS-CoV-2 infection: Focus on odorant specificity and chronic persistence

Background

Smell dysfunction has been recognized as an early symptom of SARS-CoV-2 infection, often occurring before the onset of core symptoms of the respiratory tract, fever or muscle pain. In most cases, olfactory dysfunction is accompanied by reduced sense of taste, is partial (microsmia) and seems to normalize after several weeks, however, especially in cases of virus-induced complete smell loss (anosmia), there are indications of persisting deficits even 2 months after recovery from the acute disease, pointing towards the possibility of chronic or even permanent smell reduction for a significant part of the patient population. To date, we have no knowledge on the specificity of anosmia towards specific odorants or chemicals and about the longer-term timeline of its persistence or reversal.

Methods

In this longitudinal study, 70 participants from a community in Lower Austria that had been tested positive for either IgG or IgM SARS-CoV-2 titers in June 2020 and a healthy control cohort (N = 348) underwent smell testing with a 12-item Cross-Cultural Smell Identification Test (CC-SIT), based upon items from the University of Pennsylvania Smell Identification Test (UPSIT). The test was performed in October 2020, i.e. 4 months after initial diagnosis via antibody testing. Results were analyzed using statistical tests for contingency for each smell individually in order to detect whether reacquisition of smell is dependent on specific odorant types.

Results

For all odorants tested, except the odor “smoke”, even 4 months or more after acute SARS-CoV-2 infection, participants with a positive antibody titer had a reduced sense of smell when compared to the control group. On average, while the control cohort detected a set of 12 different smells with 88.0% accuracy, the antibody-positive group detected 80.0% of tested odorants. A reduction of accuracy of detection by 9.1% in the antibody-positive cohort was detected. Recovery of the ability to smell was particularly delayed for three odorants: strawberry (encoded by the aldehyde ethylmethylphenylglycidate), lemon (encoded by citronellal, a monoterpenoid aldehyde), and soap (alkali metal salts of the fatty acids plus odorous additives) exhibit a sensitivity of detection of an infection with SARS-CoV-2 of 31.0%, 41.0% and 40.0%, respectively.

Conclusion

Four months or more after acute infection, smell performance of SARS-CoV-2 positive patients with mild or no symptoms is not fully recovered, whereby the ability to detect certain odors (strawberry, lemon and soap) is particularly affected, suggesting the possibility that these sensitivity to these smells may not only be lagging behind but may be more permanently affected.

Self-reported symptoms in French primary care SARS-CoV-2 patients: association with gender and age group

INTRODUCTION

The early identification of COVID-19 patients is of outmost importance in the current pandemic. As with other pathogens, presenting symptoms of SARS-CoV-2 may vary, depending on sociodemographic factors. We aimed to describe the clinical characteristics of COVID-19 patients by age/gender and to assess whether the diagnostic performance of these symptoms varied according to these variables.

METHODS

We analysed data from a cross-sectional study involving primary care patients undergoing RT-PCR testing in Lyon, France. Among patients who tested positive, we examined whether there was an association between age/gender and various symptoms. In addition, we calculated the diagnostic performance of the most specific symptoms (smell/taste disorder).

RESULTS

Among 1543 consecutive patients, 253 tested positive (16%). There were significant age/gender-related differences in symptoms. In middle-aged women, the diagnostic performance of smell/taste disorders were AUC = 0.65 [95%CI 0.59-0.71] and PPV = 72% [95%CI 53-87%], that is higher than in the entire sample (smell/taste disorders: AUC = 0.59 [95%CI 0.57-0.62] and PPV = 57% [95%CI 47-67%]. In contrast, the negative predictive values of smell/taste disorders were similar in both groups (85% [95%CI 81-89%] for middle-age women and 86% [95%CI 85-88%] for the entire sample).

CONCLUSION

We found significant age/gender-related differences in the clinical characteristics of COVID-19 patients. Screening strategies based on smell/taste disorders performed better in middle-aged women, but could not ensure a diagnosis of COVID-19 in any subgroup of patients. Future diagnostic strategies should use age/gender differentiated approaches.

What can the neurological manifestations of COVID-19 tell us: a meta-analysis

Background

Covid-19 became a global pandemic in 2019. Studies have shown that coronavirus can cause neurological symptoms, but clinical studies on its neurological symptoms are limited. In this meta-analysis, we aimed to summarize the various neurological manifestations that occurred in COVID-19 patients and calculate the incidence of various neurological manifestations. At the same time, we further explored the mechanism of nervous system injury and prognosis in COVID-19 patients in combination with their nervous system manifestations. This study provides a reference for early clinical identification of COVID-19 nervous system injury in the future, so as to achieve early treatment and reduce neurological sequelae.

Methods

We systematically searched all published English literature related to the neurological manifestations of COVID-19 from January 1, 2020, to April 30, 2021, in Pubmed, Embase, and Cochrane Library. The keywords used were COVID-19 and terminology related to the nervous system performance. All included studies were selected by two independent reviewers using EndNote and NoteExpress software, any disagreement was resolved by consensus or by a third reviewer, and the selected data were then collected for meta-analysis using a random-effects model.

Results

A total of 168 articles (n = 292,693) were included in the study, and the meta-analysis showed that the most common neurological manifestations of COVID-19 were myalgia(33%; 95%CI 0.30–0.37; I² = 99.17%), smell impairment(33%; 95%CI 0.28–0.38; I² = 99.40%), taste dysfunction(33%; 95%CI 0.27–0.39; I² = 99.09%), altered mental status(32%; 95%CI 0.22–0.43; I² = 99.06%), headache(29%; 95%CI 0.25–0.33; I² = 99.42%), encephalopathy(26%; 95%CI 0.16–0.38; I² = 99.31%), alteration of consciousness(13%; 95%CI 0.08–0.19; I² = 98.10%), stroke(12%; 95%CI 0.08–0.16; I² = 98.95%), dizziness(10%; 95%CI 0.08–0.13; I² = 96.45%), vision impairment(6%; 95%CI 0.03–0.09; I² = 86.82%), intracerebral haemorrhage(5%; 95%CI 0.03–0.09; I² = 95.60%), seizure(4%; 95%CI 0.02 -0.05; I² = 98.15%), encephalitis(2%; 95%CI 0.01–0.03; I² = 90.36%), Guillan-Barré Syndrome (GBS) (1%; 95%CI 0.00–0.03; I² = 89.48%).

Conclusions

Neurological symptoms are common and varied in Covid-19 infections, and a growing number of reports suggest that the prevalence of neurological symptoms may be increasing. In the future, the role of COVID-19 neurological symptoms in the progression of COVID-19 should be further studied, and its pathogenesis and assessment methods should be explored, to detect and treat early neurological complications of COVID-19 and reduce mortality.

Does BCG provide long-term protection against SARS-CoV-2 infection? A case-control study in Quebec, Canada

Background

Early in the coronavirus disease 2019 (COVID-19) pandemic, before severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines became available, it was hypothesized that BCG (Bacillus Calmette–Guérin), which stimulates innate immunity, could provide protection against SARS-CoV-2. Numerous ecological studies, plagued by methodological deficiencies, revealed a country-level association between BCG use and lower COVID-19 incidence and mortality. We aimed to determine whether BCG administered in early life decreased the risk of SARS-CoV-2 infection in adulthood and the severity of COVID-19.

Methods

This case-control study was conducted in Quebec, Canada. Cases were patients with a positive SARS-CoV-2 nucleic acid amplification test performed at two hospitals between March–October 2020. Controls were identified among patients with non-COVID-19 samples processed by the same microbiology laboratories during the same period. Enrolment was limited to individuals born in Quebec between 1956 and 1976, whose vaccine status was accessible in a computerized registry of 4.2 million BCG vaccinations.

Results

We recruited 920 cases and 2123 controls. Fifty-four percent of cases (n = 424) and 53% of controls (n = 1127) had received BCG during childhood (OR: 1.03; 95% CI: 0.89–1.21), while 12% of cases (n = 114) and 11% of controls (n = 235) had received two or more BCG doses (OR: 1.14; 95% CI: 0.88–1.46). After adjusting for age, sex, material deprivation, recruiting hospital and occupation there was no evidence of protection conferred by BCG against SARS-CoV-2 (AOR: 1.01; 95% CI: 0.84–1.21). Among cases, 77 (8.4%) needed hospitalization and 18 (2.0%) died. The vaccinated were as likely as the unvaccinated to require hospitalization (AOR: 1.01, 95% CI: 0.62–1.67) or to die (AOR: 0.85, 95% CI: 0.32–2.39).

Conclusions

BCG does not provide long-term protection against symptomatic COVID-19 or severe forms of the disease.

Correlation of olfactory dysfunction with lung involvement and severity of COVID-19

Background

Olfactory dysfunction (OD) is a significant symptom of COVID-19 and may be the earliest symptom, or it may sometimes be the only manifestation of the disease.

Aims

To investigate whether OD is correlated with chest computed tomography (CT) findings, blood test parameters, and disease severity in COVID-19 patients.

Methods

The files of COVID-19 patients were retrospectively reviewed, and the ones who had information about smelling status and CT were taken into consideration. A total of 180 patients were divided into two groups: the OD group consisted of 89 patients with self-reported OD, and the No-OD group consisted of 91 subjects who did not complain of OD. The two groups were compared for the amount of lung consolidation on CT, intensive care unit (ICU) admission, and blood test parameters (complete blood count, alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatine kinase (CK), lactate dehydrogenase (LDH), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), ferritin, D-dimer, interleukin-6 (IL-6)).

Results

The amount of lung consolidation and ICU admission were significantly higher in the No-OD group (p < 0.001 for both). White blood cell (p = 0.06), monocyte (p = 0.26), and platelet (p = 0.13) counts and hemoglobin (p = 0.63), ALT (p = 0.89), and D-dimer (p = 0.45) levels of the two groups were similar. Lymphocyte count (p = 0.01), neutrophil count (p = 0.01), and AST (p = 0.03), CK (p = 0.01), LDH (p < 0.001), CRP (p < 0.001), ESR (p < 0.001), ferritin (p < 0.001), and IL-6 (p < 0.001) levels were significantly higher in the No-OD group.

Conclusions

The patients presenting to the hospital with self-reported OD may have less lung involvement and a milder disease course compared to patients without OD on admission.

Neurological Manifestations in COVID-19 Patients: A Meta-Analysis

Common symptoms such as dizziness, headache, olfactory dysfunction, nausea, vomiting, etc. in COVID-19 patients have indicated the involvement of the nervous system. However, the exact association of the nervous system with COVID-19 infection is still unclear. Thus, we have conducted a meta-analysis of clinical studies associated with neurological problems in COVID-19 patients. We have searched for electronic databases with MeSH terms, and the studies for analysis were selected based on inclusion and exclusion criteria and quality assessment. The Stats Direct (version 3) was used for the analysis. The pooled prevalence with 95% confidence interval of various neurological manifestations reported in the COVID-19 patients was found to be headache 14.6% (12.2-17.2), fatigue 33.6% (29.5-37.8), olfactory dysfunction 26.4% (21.8-31.3), gustatory dysfunction 27.2% (22.3-32.3), vomiting 6.7% (5.5-8.0), nausea 9.8% (8.1-11.7), dizziness 6.7% (4.7-9.1), myalgia 21.4% (18.8-24.1), seizure 4.05% (2.5-5.8), cerebrovascular diseases 9.9% (6.8-13.4), sleep disorders 14.9% (1.9-36.8), altered mental status 17.1% (12.3-22.5), neuralgia 2.4% (0.8-4.7), arthralgia 19.9% (15.3-25.0), encephalopathy 23.5% (14.3-34.1), encephalitis 0.6% (0.2-1.3), malaise 38.3% (24.7-52.9), confusion 14.2% (6.9-23.5), movement disorders 5.2% (1.7-10.4), and Guillain-Barre syndrome 6.9% (2.3-13.7). However, the heterogeneity among studies was found to be high. Various neurological manifestations related to the central nervous system (CNS) and peripheral nervous system (PNS) are associated with COVID-19 patients.

Gustatory dysfunction in COVID-19 patients: a rapid systematic review on 27,687 cases

Objective: This is a rapid systematic review concerning taste alterations in 27,687 individuals infected with SARS-CoV-2, published in the worldwide literature.Material and methods: Of the 485 articles recovered, 67 eligible studies (27,687 confirmed COVID-19 cases) were included in this analysis. We analysed the prevalence of the taste alterations in patients considering the country of origin of the studies.Results: The results show strong important differences in the overall reported prevalence of taste alterations among the different countries (from 11% of Korea to 88.8% of Belgium).Conclusions: These data highlight that there is a different geographical distribution of taste alterations in COVID-19 patients. Gustatory dysfunction seems to be an understudied symptom of COVID-19 and this may explain the inconsistencies of diagnostic criteria for COVID-19 case definition. Furthermore, this diagnostic underestimation can lead to an increased risk of contagion for the whole population and for the working classes most at risk, including the dental one.

Predictive Value of Olfactory and Taste Symptoms in the Diagnosis of COVID-19: A Systematic Review and Meta-Analysis

OBJECTIVES

This study evaluated the diagnostic value of various symptoms of coronavirus disease 2019 (COVID-19) in screening for this disease.

METHODS

Two authors (working independently) comprehensively reviewed six databases (PubMed, Cochrane Database, Embase, Web of Science, Scopus, and Google Scholar) from their dates of inception until November 2020. The predictive value of patient-reported symptoms, including otolaryngologic and general symptoms, was evaluated in adults who underwent testing for COVID-19. True-positive, true-negative, false-positive, and false-negative data were extracted from each study. The methodological quality of the included studies was evaluated using the quality assessment of diagnostic accuracy studies tool (ver. 2).

RESULTS

Twenty-eight prospective and retrospective studies were included in the meta-analysis. The diagnostic odds ratio (DOR) of a change in olfaction and/or taste was 10.20 (95% confidence interval [CI], 8.43-12.34). The area under the summary receiver operating characteristic curve was 0.8. Olfactory and/or taste changes had a low sensitivity (0.57; 95% CI, 0.47-0.66) but moderate negative (0.78; 95% CI, 0.69-0.85] and positive (0.78; 95% CI, 0.66-0.87) predictive values and a high specificity (0.91; 95% CI, 0.83-0.96). Olfactory and/or taste changes had a higher diagnostic value than the other otolaryngologic symptoms, a higher DOR and specificity, and a similar or higher diagnostic value than the other general symptoms.

CONCLUSION

Among otolaryngologic symptoms, olfactory and/or taste dysfunction was the most closely associated with COVID-19 and its general symptoms, and should therefore be considered when screening for the disease.

Taste alteration in COVID-19: Significant geographical differences exist in the prevalence of the symptom

Early detection of COVID-19 is important for reduction in the spread of the disease and gustatory disturbances (GD) are known to have a strong predictive value. In the present study, we aimed to map the geographical differences in the prevalence of GD in individuals infected with SARS-CoV-2 during the first wave of COVID-19 in order to improve case identification and to facilitate prioritization. We undertook a rapid scoping review of articles published in the repository of the National Library of Medicine (MEDLINE/PubMed) and medRxiv from their inception until 3^rd September, 2020. The minimum requirements for completing a restricted systematic review were fulfilled. Of the 431 articles retrieved, 61 studies (28,374 cases confirmed with COVID-19) from 20 countries were included in the analysis. GD were most prevalent in the Americas [66.78%, 95% CI 54.77–78.79%] compared to Europe [57.18%, 95% CI 52.35–62.01%], the Middle East [38.83%, 95% CI 27.47–50.19%] and East Asia [13.1%, 95% CI 0.14–26.06%]. No differences of GD prevalence were evident between February and August 2020. The data demonstrate that there is a marked geographical distribution of GD in COVID-19 patients which, possibly, might be explained by differences in diagnostic criteria for COVID-19 case definition during the early phase of the pandemic.

Cross sectional study of the clinical characteristics of French primary care patients with COVID-19

The early identification of patients suffering from SARS-CoV-2 infection in primary care is of outmost importance in the current pandemic. The objective of this study was to describe the clinical characteristics of primary care patients who tested positive for SARS-CoV-2. We conducted a cross-sectional study between March 24 and May 7, 2020, involving consecutive patients undergoing RT-PCR testing in two community-based laboratories in Lyon (France) for a suspicion of COVID-19. We examined the association between symptoms and a positive test using univariable and multivariable logistic regression, adjusted for clustering within laboratories, and calculated the diagnostic performance of these symptoms. Of the 1561 patients tested, 1543 patients (99%) agreed to participate. Among them, 253 were positive for SARS-CoV-2 (16%). The three most frequently reported 'ear-nose-throat' and non-'ear-nose-throat' symptoms in patients who tested positive were dry throat (42%), loss of smell (36%) and loss of taste (31%), respectively fever (58%), cough (52%) and headache (45%). In multivariable analyses, loss of taste (OR 3.8 [95% CI 3.3-4.4], p-value < 0.001), loss of smell (OR 3.0 [95% CI 1.9-4.8], p < 0.001), muscle pain (OR 1.6 [95% CI 1.2-2.0], p = 0.001) and dry nose (OR 1.3 [95% CI 1.1-1.6], p = 0.01) were significantly associated with a positive result. In contrast, sore throat (OR 0.6 [95% CI 0.4-0.8], p = 0.003), stuffy nose (OR 0.6 [95% CI 0.6-0.7], p < 0.001), diarrhea (OR 0.6 [95% CI 0.5-0.6], p < 0.001) and dyspnea (OR 0.5 [95% CI 0.3-0.7], p < 0.001) were inversely associated with a positive test. The combination of loss of taste or smell had the highest diagnostic performance (OR 6.7 [95% CI 5.9-7.5], sensitivity 44.7% [95% CI 38.4-51.0], specificity 90.8% [95% CI 89.1-92.3]). No other combination of symptoms had a higher performance. Our data could contribute to the triage and early identification of new clusters of cases.

Prevalence and prognosis of otorhinolaryngological symptoms in patients with COVID-19: a systematic review and meta-analysis

Objective

A systematic review and meta-analysis were performed to evaluate the prevalence and prognosis of otorhinolaryngological symptoms in patients with the diagnosed coronavirus disease 2019 (COVID-19).

Methods

A systematic search of PubMed, Embase, Web of Science, and Google Scholar databases was performed up to August 19, 2020.We included studies that reported infections with COVID-19 and symptoms of otolaryngology. The retrieved data from the respective studies were evaluated and summarized. The study's immediate result was to assess the combined prevalence of otorhinolaryngological symptoms in patients with COVID-19. However, the secondary result was to determine the exacerbation of COVID-19 infection in patients with otorhinolaryngological symptoms.

Results

Fifty-four studies with 16,478 patients were included. Olfactory dysfunction, sneezing and sputum production were the 3 most prevalent otorhinolaryngological symptoms in patients with COVID-19. The pooled prevalence amongst the prevalent symptoms was 47% (95% CI 29–65; range 0–98; I² = 99.58%), 27% (95% CI 11–48; range 12–40; I² = 93.34%), and 22% (95% CI 16–30; range 2–56; I² = 97.60%), respectively. The proportion of severely ill patients with sputum production and shortness of breath was significantly higher among patients with COVID-19 infections (OR 1.66 [95% CI 1.08–2.54]; P = 0.02, I² = 51% and 3.29 [95% CI 1.57–6.90]; P = 0.002, I² = 49%, respectively). Subgroup analysis showed no statistically significant differences between the incidence of otolaryngology symptoms in severely ill patients and non-severely ill patients (OR 1.43 [95% CI 1.12–1.82]; P = 0.07 I² = 53.1%). In contrast, the incidence of shortness of breath in severely ill patients was significantly increased (3.29 [1.57–6.90]; P = 0.002, I² = 49%).

Conclusion

Our research shows that otorhinolaryngology symptoms in patients with COVID-19 are not uncommon, which should attract otorhinolaryngologists' attention.

Retronasal olfactory testing in early diagnosed and suspected COVID-19 patients: a 7-week follow-up study

OBJECTIVES

Olfactory dysfunction (OD) constitutes a major symptom in Coronavirus Disease 2019 (COVID-19). Yet, most data on smell loss rely on the evaluation of orthonasal olfactory performance. Therefore, we aimed to assess retronasal olfactory function (ROF) over a period of several weeks in proven and suspected COVID-19 patients.

METHODS

One hundred and one subjects with suspected or laboratory-proven COVID-19 participated in this study. In patients with OD no longer than 4 weeks after initial symptom onset, ROF was measured with the 7-item Candy Smell Test ten times over 7 weeks.

RESULTS

Olfactory function was decreased in the investigated patients and remained decreased over the course of 7 weeks. One-way repeated-measures ANOVA revealed no significant difference of ROF between different measurement time points. However, self-assessment of smell and flavour improved significantly (p = 0.013 and p = 0.043), but did not show complete recovery.

CONCLUSION

The current investigation revealed significant improvements in subjective smell and flavour perception over the course of 7 weeks in proven and suspected COVID-19 patients suffering from acute OD. However, objectively measured ROF based on a screening test revealed no improvements within the same time period.

SARS-CoV-2 Induced Neurological Manifestations Entangles Cytokine Storm That Implicates For Therapeutic Strategies

The new coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), can present with neurological symptoms and induce neurological complications. The involvement in both the central and peripheral nervous systems in COVID-19 patients has been associated with direct invasion of the virus and the induction of cytokine storm. This review discussed the pathways for the virus invasion into the nervous system and characterized the SARS-CoV-2 induced cytokine storm. In addition, the mechanisms underlying the immune responses and cytokine storm induction after SARS-CoV-2 infection were also discussed. Although some neurological symptoms are mild and disappear after recovery from infection, some severe neurological complications contribute to the mortality of COVID-19 patients. Therefore, the insight into the cause of SARS-CoV-2 induced cytokine storm in context with neurological complications will formulate the novel management of the disease and further identify new therapeutic targets for COVID-19.

Geographical Variations in Host Predisposition to COVID-19 Related Anosmia, Ageusia, and Neurological Syndromes

The novel coronavirus disease (COVID-19), has become the most critical global health challenge in recent history. With SARS-CoV-2 infection, there was an unexpectedly high and specific prevalence of olfactory and taste disorders (OTDs). These high rates of hyposmia and hypogeusia, initially reported as up to 89% in European case series, led to the global inclusion of loss of taste and/or smell as a distinctive feature of COVID-19. However, there is emerging evidence that there are striking differences in the rates of OTDs in East Asian countries where the disease first emerged, as compared to Western countries (15.8 vs. 60.9%, p-value < 0.01). This may be driven by either variations in SARS-CoV-2 subtypes presenting to different global populations or genotypic differences in hosts which alter the predisposition of these different populations to the neuroinvasiveness of SARS-CoV-2. We also found that rates of OTDs were significantly higher in objective testing for OTDs as compared to subjective testing (73.6 vs. 60.8%, p-value = 0.03), which is the methodology employed by most studies. Concurrently, it has also become evident that racial minorities across geographically disparate world populations suffer from disproportionately higher rates of COVID-19 infection and mortality. In this mini review, we aim to delineate and explore the varying rates of olfactory and taste disorders amongst COVID-19 patients, by focusing on their underlying geographical, testing, ethnic and socioeconomic differences. We examine the current literature for evidence of differences in the olfactory and gustatory manifestations of COVID-19 and discuss current pathophysiological hypotheses for such differences.

Contribution of Pro-Inflammatory Molecules Induced by Respiratory Virus Infections to Neurological Disorders

Neurobehavioral alterations and cognitive impairment are common phenomena that represent neuropsychiatric disorders and can be triggered by an exacerbated immune response against pathogens, brain injury, or autoimmune diseases. Pro-inflammatory molecules, such as cytokines and chemokines, are produced in the brain by resident cells, mainly by microglia and astrocytes. Brain infiltrating immune cells constitutes another source of these molecules, contributing to an impaired neurological synapse function, affecting typical neurobehavioral and cognitive performance. Currently, there is increasing evidence supporting the notion that behavioral alterations and cognitive impairment can be associated with respiratory viral infections, such as human respiratory syncytial virus, influenza, and SARS-COV-2, which are responsible for endemic, epidemic, or pandemic outbreak mainly in the winter season. This article will review the brain′s pro-inflammatory response due to infection by three highly contagious respiratory viruses that are the leading cause of acute respiratory illness, morbidity, and mobility in infants, immunocompromised and elderly population. How these respiratory viral pathogens induce increased secretion of pro-inflammatory molecules and their relationship with the alterations at a behavioral and cognitive level will be discussed.

Simultaneously complete but not partial taste and smell losses were associated with SARS-CoV-2 infection

Objectives

The aim of this study was to investigate the association between taste and smell losses and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, and to elucidate whether taste preference influences such taste loss.

Methods

A matched case–control study was conducted in 366 Thai participants, including 122 who were confirmed SARS-CoV-2-positive by RT-PCR (case group) and 244 who were SARS-CoV-2-negative (control group). Taste, smell, and appetite changes were assessed by self-reported visual analog scale. Preference for sweet, salty, umami, sour, bitter, and spicy were judged using the validated TASTE-26 questionnaire.

Results

Partial taste and smell losses were observed in both groups, while complete losses (ageusia and anosmia) were detected only in the case group. Moreover, only ageusia and anosmia were associated with SARS-CoV-2 positivity (P < 0.001, odds ratio of 14.5 and 27.5, respectively). Taste, smell, and appetite scores were more severely reduced in the case group (P < 0.0001). Multivariate analysis showed that anosmia and ageusia were the best predictors of SARS-CoV-2 positivity, followed by appetite loss and fever. Simultaneous losses of taste and smell but not taste preferences were associated with SARS-CoV-2 positivity (P < 0.01, odds ratio 2.28).

Conclusions

Complete, but not partial, losses of taste and smell were the best predictors of SARS-CoV-2 infection. During the current COVID-19 pandemic, healthy persons with sudden simultaneous complete loss of taste and smell should be screened for COVID-19.

Diagnostic Value of Patient-Reported and Clinically Tested Olfactory Dysfunction in a Population Screened for COVID-19

Importance

Recent studies have suggested that olfactory dysfunction and gustatory dysfunction are associated with coronavirus disease 2019 (COVID-19). However, olfaction has been evaluated solely on reported symptoms, after COVID-19 diagnosis, and in both mild and severe COVID-19 cases, but rarely has it been assessed in prospectively unselected populations.

Objective

To evaluate the diagnostic value of a semiobjective olfactory test developed to assess patient-reported chemosensory dysfunction prior to testing for the presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in patients attending a COVID-19 screening facility.

Design, Setting, and Participants

This prospective diagnostic study with participants and observers blinded to COVID-19 status was conducted in a COVID-19 screening center of a tertiary university hospital in France from March 23 to April 22, 2020. Participants were 854 consecutively included health care workers or outpatients with symptoms or with close contact with an index case. Exclusion criteria were prior chemosensory dysfunction, testing inability, or contraindications (n = 45).

Main Outcomes and Measures

Participants were interviewed to ascertain their symptoms and then underwent Clinical Olfactory Dysfunction Assessment (CODA), an ad hoc test developed for a simple and fast evaluation of olfactory function. This assessment followed a standardized procedure in which participants identified and rated the intensity of 3 scents (lavender, lemongrass, and mint) to achieve a summed score ranging from 0 to 6. The COVID-19 status was assessed using reverse transcriptase-polymerase chain reaction to detect the presence of SARS-CoV-2 in samples collected via nasopharyngeal swab (reference standard) to calculate the diagnostic values of patient-reported chemosensory dysfunction and CODA.

Results

Of 809 participants, the female to male sex ratio was 2.8, and the mean (SD) age was 41.8 (13.0) years (range, 18-94 years). All participants, if symptomatic, had mild disease at the time of testing, and 58 (7.2%) tested positive for SARS-CoV-2. Chemosensory dysfunction was reported by 20 of 58 participants (34.5%) with confirmed COVID-19 vs 29 of 751 participants (3.9%) who tested negative for COVID-19 (absolute difference, 30.6% [95% CI, 18.3%-42.9%]). Olfactory dysfunction, either self-reported or clinically ascertained (CODA score ≤3), yielded similar sensitivity (0.31 [95% CI, 0.20-0.45] vs 0.34 [95% CI, 0.22-0.48]) and specificity (0.97 [95% CI, 0.96-0.98) vs 0.98 [95% CI, 0.96-0.99]) for COVID-19 diagnosis. Concordance was high between reported and clinically tested olfactory dysfunction, with a Gwet AC1 of 0.95 (95% CI, 0.93-0.97). Of 19 participants, 15 (78.9%) with both reported olfactory dysfunction and a CODA score of 3 or lower were confirmed to have COVID-19. The CODA score also revealed 5 of 19 participants (26.3%) with confirmed COVID-19 who had previously unperceived olfactory dysfunction.

Conclusions and Relevance

In this prospective diagnostic study of outpatients with asymptomatic or mild to moderate COVID-19, systematically assessed anamnesis and clinical testing with the newly developed CODA were complementary and specific for chemosensory dysfunction. Olfactory dysfunction was suggestive of COVID-19, particularly when clinical testing confirmed anamnesis. However, normal olfaction was most common among patients with COVID-19.

Comparative Study of Chemosensory Dysfunction in COVID-19 in 2 Geographically Distinct Regions

OBJECTIVE

To directly compare the prevalence of chemosensory dysfunction (smell and taste) in geographically distinct regions with the same questionnaires.

METHODS

A cross-sectional study was performed to evaluate the self-reported symptoms among adults (older than 18 years) who underwent COVID-19 testing at an ambulatory assessment center in Canada and at a hospital in Israel between March 16, 2020, and August 19, 2020. The primary outcome was the prevalence of self-reported chemosensory dysfunction (anosmia/hypomsia and dysgeusia/ageusia). Subgroup analysis was performed to evaluate the prevalence of chemosensory deficits among the outpatients.

RESULTS

We identified a total of 350 COVID-19-positive patients (138 Canadians and 212 Israelis). The overall prevalence of chemosensory dysfunction was 47.1%. There was a higher proportion of chemosensory deficits among Canadians compared to Israelis (66.7% vs 34.4%, P < .01). A subgroup analysis for outpatients (never hospitalized) still identified a higher prevalence of chemosensory dysfunction among Canadians compared to Israelis (68.2% vs 36.1%, P < 0.01). A majority of patients recovered their sense of smell after 4 weeks of symptom onset.

CONCLUSION

Although the prevalence of chemosensory deficit in COVID-19 was found to be similar to previously published reports, the prevalence can vary significantly across different geographical regions. Therefore, it is important to obtain regionally specific data so that the symptom of anosmia/dysgeusia can be used as a guide for screening for the clinical diagnosis of COVID-19.