Viral Pneumonia Requiring Differentiation from Acute and Progressive Diffuse Interstitial Lung Diseases

Predictive Factors for Invasive Mechanical Ventilation in Community-Acquired Pneumonia

Objective Community-acquired pneumonia is an acute infectious disease with potentialy life-threatening consequences. Because invasive mechanical ventilation (IMV) requires the attention of many medical staff, early risk prediction at the time of admission is expected to lead to a predictable course of patient care and the appropriate allocation of medical resources. There are a limited number of reports on predictive factors for IMV, such as SMART-COP. Therefore, further studies are required. Patients and Methods We retrospectively reviewed cases of patients with community-acquired pneumonia other than COVID-19 admitted to our institution from 2002 to 2019. We performed competing risks analysis with the need for IMV from the day after admission as the outcome and used multivariable analysis to identify predictive factors of IMV from admission characteristics. Results Among 2,227 patients (mean age 67.3 years, 69.0% male), 39 patients required IMV on or after the day following admission. A multivariable analysis showed that predictive factors of IMV were respiratory rate >30 breaths/min [subdistribution hazard ratio (SHR), 5.53; 95% confidence interval (CI), 2.09 to 14.67; p=0.001], PaO2/FiO2 ratio <250 (SHR, 8.02; 95% CI, 2.78 to 23.13; p<0.001), and Legionella pneumonia (SHR, 4.87; 95% CI, 1.56 to 15.13; p=0.006). Conclusion This study revealed that among other factors including mainly vital signs, specific infection by a microorganism itself (Legionella in this study) was a predictive factor for the need of IMV.

Prognostic factors of virus-associated pneumonia other than COVID-19 in adults

OBJECTIVE

To determine prognostic factors of virus-associated pneumonia other than coronavirus disease 2019.

METHODS

We retrospectively studied patients suffering from virus-associated community-acquired pneumonia, and who were admitted to Saitama Cardiovascular and Respiratory Center from 2002 to 2020. Prognostic factors were analyzed by univariable and multivariable regression analysis of patient demographics, laboratory data, chest imaging, severity on admission, and initial treatment.

PATIENTS

HIV-positive patients, those with non-resected lung cancer or receiving chemotherapy, and those with COVID-19 were excluded. Included were 363 patients diagnosed by nucleic acid amplification method, paired sera, and rapid diagnostic tests.

RESULTS

A CURB-65 score of ≥3 was significant by univariable analysis for 60-day mortality but was nonsignificant by multivariable analysis. The poor prognostic factors that were significant by multivariable analysis (p < 0.05) included immunosuppressive state due to systemic corticosteroid or immunosuppressant administration, acute kidney injury on admission, and corticosteroid administration initiated within 5 days or 5 days to 2 weeks from onset.

CONCLUSION

A CURB-65 score of ≥3, which is considered to indicate severe pneumonia, was of limited value for predicting mortality of virus-associated pneumonia. We showed patients' underlying diseases and complications to be independent factors of poor prognosis for 60-day mortality. Timing of the initiation of corticosteroid administration remains to be elucidated.

Histologic Characteristics and Clinical Courses of Primary Viral Pneumonia Other than COVID-19

Objective To clarify both the histologic changes in primary viral pneumonia other than COVID-19 and whether patients with severe lung injury (SLI) on biopsy specimens progress to severe respiratory insufficiency. Methods Patients with primary viral pneumonia other than COVID-19, who underwent lung tissue biopsy, were retrospectively studied. Patients Forty-three patients (41 living patients and 2 autopsied cases) were included in the study. Results Nine patients had SLI, whereas most of patients who recovered from primary viral pneumonia showed a nonspecific epithelial injury pattern. One patient underwent a biopsy under mechanical ventilation. Two of 8 (25.0%) patients on ambient air or low-flow oxygen therapy progressed to a severe respiratory condition and then to death, while only 1 (3.1%) of 32 patients without SLI progressed to a severe respiratory condition and death (p=0.096). The proportion of patients who required O2 treatment for ≥2 weeks was higher in patients with SLI than in those without SLI (p=0.033). The 2 autopsy cases showed a typical pattern of diffuse alveolar damage, with both showing hyaline membranes. Non-specific histologic findings were present in 32 patients without SLI. Conclusion Some patients with SLI progressed to severe respiratory insufficiency, whereas those without SLI rarely progressed to severe respiratory insufficiency or death. The frequency of patients progressing to a severe respiratory condition or death did not differ significantly between those with and without SLI. The proportion of patients who required longer O2 treatment was higher in SLI group than in those without SLI.

Respiratory virus infections of the lower respiratory tract elevate bronchoalveolar lavage eosinophil fraction: a clinical retrospective study and case review

BACKGROUND

Eosinophilic airway inflammation caused by respiratory virus infection has been demonstrated in basic research; however, clinical investigations are lacking. To clarify the extent to which respiratory virus infection induces airway eosinophilic inflammation, we reviewed the results of bronchoalveolar lavage (BAL) and respiratory virus testing performed at our hospital.

METHODS

Among the BAL procedures performed at the University of the Ryukyu Hospital from August 2012 to September 2016, we collected cases of acute respiratory disease in which multiplex polymerase chain reaction (PCR) was used to search for respiratory viruses. The effect of respiratory virus detection on BAL eosinophil fraction was analyzed using statistical analysis. A case study was conducted on respiratory virus detection, which showed an elevated BAL eosinophil fraction.

RESULTS

A total of 95 cases were included in this study, of which 17 were PCR-positive. The most common respiratory virus detected was parainfluenza virus (eight cases). The PCR-positive group showed a higher BAL eosinophil fraction than the PCR-negative group (p = 0.030), and more cases had a BAL eosinophil fraction > 3% (p = 0.017). Multivariate analysis revealed that being PCR-positive was significantly associated with BAL eosinophil fraction > 1% and > 3%. There were nine PCR-positive cases with a BAL eosinophil fraction > 1%, of which two cases with parainfluenza virus infection had a marked elevation of BAL eosinophil fraction and were diagnosed with eosinophilic pneumonia.

CONCLUSIONS

Cases of viral infection of the lower respiratory tract showed an elevated BAL eosinophil fraction. The increase in eosinophil fraction due to respiratory virus infection was generally mild, whereas some cases showed marked elevation and were diagnosed with eosinophilic pneumonia. Respiratory virus infection is not a rare cause of elevated BAL eosinophil fraction and should be listed as a differential disease in the practice of eosinophilic pneumonia.

Characteristics of patients with viral infections of the lower respiratory tract: A retrospective study

While the impact of respiratory virus infections has been well researched in some respiratory diseases, no clinical studies have discussed the subject of who would be more likely to develop respiratory virus infections among patients with various respiratory illnesses who come from different backgrounds. This study aimed to identify respiratory diseases that are frequently associated with respiratory virus infections along with the characteristics of patients who develop such infections in clinical settings. Tested specimens were obtained from the lower respiratory tract by bronchoscopy to provide more accurate data. Data of bronchoscopies at Ryukyu University Hospital between August 2012 and September 2016 were reviewed, and patients who underwent multiplex polymerase chain reaction (PCR) tests for detecting respiratory viruses in bronchoscopy specimens were retrospectively recruited for descriptive statistics. Differences among patients' primary pulmonary diseases and backgrounds were compared between the PCR-positive and -negative patients, and multivariate statistical analysis was performed to analyze factors associated with a positive PCR test result. Overall, 756 bronchoscopies were performed during the study period and PCR tests were performed for 177 patients. Of them, 27 tested positive for respiratory viruses, mainly parainfluenza virus and rhinovirus, and out of those, 7 were hospitalized for >1 month. Overall, all patients did not experience typical upper respiratory infection symptoms. In positive patients, 13 and 7 had diagnoses of interstitial lung disease and bacterial pneumonia, respectively. The diagnoses of 3 bacterial pneumonia cases were changed to viral pneumonia after receiving their PCR-positive tests. Respiratory virus infections were confirmed in 14 patients on immunosuppressant therapy and 4 on maintenance dialysis. Multivariate analysis revealed that immunosuppressant therapy and maintenance dialysis were independently associated with respiratory virus infections. Viruses were commonly detected in patients with interstitial lung diseases and bacterial pneumonia, while few patients were diagnosed with pure viral pneumonia. These illnesses were considered to be induced by respiratory infections. Immunosuppressant therapy and maintenance dialysis were associated with respiratory virus infections. Multiplex PCR testing is an essential diagnostic tool for respiratory virus infections in immunocompromised patients.

Hydroxychloroquine on the Pulmonary Vascular Diseases in Interstitial Lung Disease: Immunologic Effects, and Virus Interplay

To investigate the effects of hydroxychloroquine (HCQ) drug use on the risk of pulmonary vascular disease (PVD) in an interstitial lung disease cohort (ILD cohort, ILD+ virus infection), we retrospectively enrolled the ILD cohort with HCQ (HCQ users, N = 4703) and the ILD cohort without HCQ (non-HCQ users, N = 4703) by time-dependence after propensity score matching. Cox models were used to analyze the risk of PVD. We calculated the adjusted hazard ratios (aHRs) and their 95% confidence intervals (CIs) for PVD after adjusting for sex, age, comorbidities, index date and immunosuppressants, such as steroids, etc. Compared with the HCQ nonusers, in HCQ users, the aHRs (95% CIs) for PVD were (2.24 (1.42, 3.54)), and the women’s aHRs for PVD were (2.54, (1.49, 4.35)). The aHRs based on the days of HCQ use for PVD of 28−30 days, 31−120 days, and >120 days were (1.27 (0.81, 1.99)), (3.00 (1.81, 4.87)) and (3.83 (2.46, 5.97)), respectively. The medium or long-term use of HCQ or young women receiving HCQ were associated with a higher aHR for PVD in the ILD cohort. These findings indicated interplay of the primary immunologic effect of ILD, comorbidities, women, age and virus in the HCQ users.

Developing a pneumonia diagnosis ontology from multiple knowledge sources

Background: Pneumonia is difficult to differentiate from other pulmonary diseases because it shares many symptoms with these diseases. Diagnosing pneumonia in clinical practice would benefit from having access to a codified representation of clinical knowledge. An ontology represents a well-established paradigm for such codification. Objectives: The goal of this research is to create Pneumonia Diagnosis Ontology (PNADO) that brings together the medical knowledge dispersed among multiple medical knowledge sources. Material and Methods: We used several clinical practice guidelines (CPGs) describing the pneumonia diagnostic process as a starting point in developing PNADO. Preliminary version of PNADO was subsequently expanded to cover a broader range of the concepts by reusing ontologies from Open Biological and Biomedical Ontology (OBO) Foundry and BioPortal. PNADO was evaluated by examining relevant concepts from the pneumonia-specific systematic reviews, using patient data from the MIMIC-III clinical dataset, and by clinical domain experts. Results: PNADO is a comprehensive ontology and has a rich set of classes and properties that cover different types of pneumonia, pathogens, symptoms, clinical signs, laboratory tests and imaging, clinical findings, complications, and diagnoses. Conclusion: PNADO unifies pneumonia diagnostic concepts from multiple knowledge sources. It is available in the BioPortal repository.

Community-acquired Respiratory Virus Cases Mimic COVID-19 on Lung Computed Tomography

We herein report four patients with community-acquired respiratory virus (CRV) infection. Although they had no history of contact with any individual with coronavirus disease 2019 (COVID-19), they were suspected of having COVID-19 based on findings of high-resolution computed tomography (CT) of the lungs. Among the four patients, two were infected with rhinovirus, one with metapneumovirus, and one with influenza A. Their chest CT findings were similar to those of COVID-19 patients reported in previous studies. Both CRV infection and COVID-19 can show various patterns on chest CT. CRV infection is thus indistinguishable from COVID-19 based on CT findings alone.

Frequency and Significance of Coinfection in Patients with COVID-19 at Hospital Admission

Objective Viral pneumonia is not rare in community-acquired pneumonia (CAP). Mixed or secondary pneumonia (coinfection) can be seen in viral pneumonia; however, its frequency in coronavirus disease 2019 (COVID-19) has only been investigated in a few studies of short duration, and its significance has not been fully elucidated. We investigated the frequency and significance of co-infection in patients with COVID-19 over a 1-year study period. Methods Coinfection was investigated via multiplex polymerase chain reaction (PCR), culture of respiratory samples, rapid diagnostic tests, and paired sera. We used logistic regression analysis to analyze the effect of coinfection on severity at admission and Cox proportional-hazards model analysis to analyze the effect of coinfection on need for high-flow nasal cannula, invasive mandatory ventilation use, and death, respectively. Patients We retrospectively investigated 298 patients who suffered CAP due to severe acute respiratory syndrome coronavirus-2 infection diagnosed by PCR and were admitted to our institution from February 2020 to January 2021. Results Primary viral pneumonia, and mixed viral and bacterial pneumonia, accounted for 90.3% and 9.7%, respectively, of COVID-19-associated CAP, with viral coinfection found in 30.5% of patients with primary viral pneumonia. Influenza virus was the most common (9.4%). Multivariable analysis showed coinfection not to be an independent factor of severity on admission, need for high-flow nasal cannula or invasive mandatory ventilation, and mortality. Conclusion Viral coinfection was common in COVID-19-associated CAP. Severity on admission, need for high-flow oxygen therapy or invasive mandatory ventilation, and mortality were not affected by coinfection.

Novel insights into the pathogenesis of virus-induced ARDS: review on the central role of the epithelial-endothelial barrier

Introduction: Respiratory viruses can directly or indirectly damage the pulmonary defense barrier, potentially contributing to acute respiratory distress syndrome (ARDS). Despite developments in the understanding of the pathogenesis of ARDS, the underlying pathophysiology still needs to be elucidated.Areas covered: The PubMed database was reviewed for relevant papers published up to 2021. This review summarizes the currently immunological and clinical studies to provide a systemic overview of the epithelial-endothelial barrier, given the recently published immunological profiles upon viral pneumonia, and the potentially detrimental contribution to respiratory function caused by damage to this barrier.Expert opinion: The biophysical structure of host pulmonary defense is intrinsically linked with the ability of alveolar epithelial and capillary endothelial cells, known as the epithelial-endothelial barrier, to respond to, and instruct the delicate immune system to protect the lungs from infections and injuries. Recently published immunological profiles upon viral infection, and its contributions to the damage of respiratory function, suggest a central role for the pulmonary epithelial and endothelial barrier in the pathogenesis of ARDS. We suggest a central role and common pathways by which the epithelial-endothelial barrier contributes to the pathogenesis of ARDS.

Ground-glass opacity (GGO): a review of the differential diagnosis in the era of COVID-19

Thoracic imaging is fundamental in the diagnostic route of Coronavirus disease 2019 (COVID-19) especially in patients admitted to hospitals. In particular, chest computed tomography (CT) has a key role in identifying the typical features of the infection. Ground-glass opacities (GGO) are one of the main CT findings, but their presence is not specific for this viral pneumonia. In fact, GGO is a radiological sign of different pathologies with both acute and subacute/chronic clinical manifestations. In the evaluation of a subject with focal or diffuse GGO, the radiologist has to know the patient’s medical history to obtain a valid diagnostic hypothesis. The authors describe the various CT appearance of GGO, related to the onset of symptoms, focusing also on the ancillary signs that can help radiologist to obtain a correct and prompt diagnosis.

Quantitative Evaluation of COVID-19 Pneumonia Lung Extension by Specific Software and Correlation with Patient Clinical Outcome

Lung infection named as COVID-19 is an infectious disease caused by the most recently discovered coronavirus 2 (SARS-CoV-2). CT (computed tomography) has been shown to have good sensitivity in comparison with RT-PCR, particularly in early stages. However, CT findings appear to not always be related to a certain clinical severity. The aim of this study is to evaluate a correlation between the percentage of lung parenchyma volume involved with COVID-19 infection (compared to the total lung volume) at baseline diagnosis and correlated to the patient's clinical course (need for ventilator assistance and or death). All patients with suspected COVID-19 lung disease referred to our imaging department for Chest CT from 24 February to 6 April 2020were included in the study. Specific CT features were assessed including the amount of high attenuation areas (HAA) related to lung infection. HAA, defined as the percentage of lung parenchyma above a predefined threshold of -650 (HAA%, HAA/total lung volume), was automatically calculated using a dedicated segmentation software. Lung volumes and CT findings were correlated with patient's clinical course. Logistic regressions were performed to assess the predictive value of clinical, inflammatory and CT parameters for the defined outcome. In the overall population we found an average infected lung volume of 31.4 ± 26.3% while in the subgroup of patients who needed ventilator assistance and who died as well as the patients who died without receiving ventilator assistance the volume of infected lung was significantly higher 41.4 ± 28.5 and 72.7 ± 36.2 (p < 0.001). In logistic regression analysis best predictors for ventilation and death were the presence of air bronchogram (p = 0.006), crazy paving (p = 0.007), peripheral distribution (p < 0.001), age (p = 0.002), fever at admission (p = 0.007), dyspnea (p = 0.002) and cardiovascular comorbidities (p < 0.001). In multivariable analysis, quantitative CT parameters and features added incremental predictive value beyond a model with only clinical parameters (area under the curve, 0.78 vs. 0.74, p = 0.02). Our study demonstrates that quantitative evaluation of lung volume involved by COVID-19 pneumonia helps to predict patient's clinical course.

Two Cases of Primary Rhinovirus Pneumonia with Multiple Pulmonary Nodules

Two patients, a 60-year-old man and 43-year-old woman, presented to our hospital with symptoms of respiratory tract infection. These patients showed imaging findings of multiple small nodules, ground-glass opacities, and consolidations. In case 1, although antibiotics were started, bilateral shadows spread widely, which made us suspect interstitial pneumonia. The condition improved after steroid administration, and there has been no recurrence since completing this treatment. In case 2, the patient recovered rapidly with antibiotics only. In both cases, we performed bronchoalveolar lavage, in which only human rhinovirus infection was detected by multiplex polymerase chain reaction testing, and primary rhinovirus pneumonia was diagnosed.

COVID-19 disease: CT Pneumonia Analysis prototype by using artificial intelligence, predicting the disease severity

Background

Since the beginning of 2020, coronavirus disease has spread widely all over the world and this required rapid adequate management; therefore, continuous searching for rapid and sensitive CT chest techniques was needed to give a hand for the clinician.

We aimed to assess the validity of computed tomography (CT) quantitative and qualitative analysis in COVID-19 pneumonia and how it can predict the disease severity on admission.

Results

One hundred and twenty patients were enrolled in our study, 98 (81.7%) of them were males, and 22 (18.3%) of them were females with a mean age of 52.63 ± 12.79 years old, ranging from 28 to 83 years. Groups B and C showed significantly increased number of involved lung segments and lobes, frequencies of consolidation, crazy-paving pattern, and air bronchogram. The total lung severity score and the total score for crazy-paving and consolidation are used as severity indicators in the qualitative method and could differentiate between groups B and C and group A (90.9% sensitivity, 87.5% specificity, and 93.2% sensitivity, 87.5% specificity, respectively), while the quantitative indicators could differentiate these three groups. Using the quantitative CT indicators, the validity to differentiate different groups showed 84.1% sensitivity and 81.2% specificity for the opacity score, and 90.9% sensitivity and 81.2% specificity for the percentage of high opacity.

Conclusion

Advances in CT COVID-19 pneumonia assessment provide an accurate and rapid tool for severity assessment, helping for decision-making notably for the critical cases.

COVID-19: A Great Mime or a Trigger Event of Autoimmune Manifestations?

Viruses can induce autoimmune diseases, in addition to genetic predisposition and environmental factors. Particularly, coronaviruses are mentioned among the viruses implicated in autoimmunity. Today, the world's greatest threat derives from the pandemic of a new human coronavirus, called "severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the responsible agent of coronavirus disease 2019 (COVID-19). First case of COVID-19 was identified in Wuhan, the capital of Hubei, China, in December 2019 and quickly spread around the world. This review focuses on autoimmune manifestations described during COVID-19, including pro-thrombotic state associated with antiphospholipid antibodies (aPL), acute interstitial pneumonia, macrophage activation syndrome, lymphocytopenia, systemic vasculitis, and autoimmune skin lesions. This offers the opportunity to highlight the pathogenetic mechanisms common to COVID-19 and several autoimmune diseases in order to identify new therapeutic targets. In a supposed preliminary pathogenetic model, SARS-CoV-2 plays a direct role in triggering widespread microthrombosis and microvascular inflammation, because it is able to induce transient aPL, endothelial damage and complement activation at the same time. Hence, endothelium might represent the common pathway in which autoimmunity and infection converge. In addition, autoimmune phenomena in COVID-19 can be explained by regulatory T cells impairment and cytokines cascade.

Multimodality imaging of COVID-19 pneumonia: from diagnosis to follow-up. A comprehensive review

Due to its pandemic diffusion, SARS- CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2) infection represents a global threat. Despite a multiorgan involvement has been described, pneumonia is the most common manifestation of COVID-19 (Coronavirus disease 2019) and it is associated with a high morbidity and a considerable mortality. Especially in the areas with high disease burden, chest imaging plays a crucial role to speed up the diagnostic process and to aid the patient management. The purpose of this comprehensive review is to understand the diagnostic capabilities and limitations of chest X-ray (CXR) and high-resolution computed tomography (HRCT) in defining the common imaging features of COVID-19 pneumonia and correlating them with the underlying pathogenic mechanisms. The evolution of lung abnormalities over time, the uncommon findings, the possible complications, and the main differential diagnosis occurring in the pandemic phase of SARS-CoV-2 infection are also discussed.

Imaging Diagnostics and Pathology in SARS-CoV-2-Related Diseases

In December 2019, physicians reported numerous patients showing pneumonia of unknown origin in the Chinese region of Wuhan. Following the spreading of the infection over the world, The World Health Organization (WHO) on 11 March 2020 declared the novel severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) outbreak a global pandemic. The scientific community is exerting an extraordinary effort to elucidate all aspects related to SARS-CoV-2, such as the structure, ultrastructure, invasion mechanisms, replication mechanisms, or drugs for treatment, mainly through in vitro studies. Thus, the clinical in vivo data can provide a test bench for new discoveries in the field of SARS-CoV-2, finding new solutions to fight the current pandemic. During this dramatic situation, the normal scientific protocols for the development of new diagnostic procedures or drugs are frequently not completely applied in order to speed up these processes. In this context, interdisciplinarity is fundamental. Specifically, a great contribution can be provided by the association and interpretation of data derived from medical disciplines based on the study of images, such as radiology, nuclear medicine, and pathology. Therefore, here, we highlighted the most recent histopathological and imaging data concerning the SARS-CoV-2 infection in lung and other human organs such as the kidney, heart, and vascular system. In addition, we evaluated the possible matches among data of radiology, nuclear medicine, and pathology departments in order to support the intense scientific work to address the SARS-CoV-2 pandemic. In this regard, the development of artificial intelligence algorithms that are capable of correlating these clinical data with the new scientific discoveries concerning SARS-CoV-2 might be the keystone to get out of the pandemic.

Diffuse alveolar damage (DAD) resulting from coronavirus disease 2019 Infection is Morphologically Indistinguishable from Other Causes of DAD

Aims

Diffuse alveolar damage (DAD) is a ubiquitous finding in inpatient coronavirus disease 2019 (COVID‐19)‐related deaths, but recent reports have also described additional atypical findings, including vascular changes. An aim of this study was to assess lung autopsy findings in COVID‐19 inpatients, and in untreated severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2)‐positive individuals who died in the community, in order to understand the relative impact of medical intervention on lung histology. Additionally, we aimed to investigate whether COVID‐19 represents a unique histological variant of DAD by comparing the pathological findings with those of uninfected control patients.

Methods and results

Lung sections from autopsy cases were reviewed by three pulmonary pathologists, including two who were blinded to patient cohort. The cohorts included four COVID‐19 inpatients, four cases with postmortem SARS‐CoV‐2 diagnoses who died in the community, and eight SARS‐CoV‐2‐negative control cases. DAD was present in all but one SARS‐CoV‐2‐positive patient, who was asymptomatic and died in the community. Although SARS‐CoV‐2‐positive patients were noted to have more focal perivascular inflammation/endothelialitis than control patients, there were no significant differences in the presence of hyaline membranes, fibrin thrombi, airspace organisation, and ‘acute fibrinous and organising pneumonia’‐like intra‐alveolar fibrin deposition between the cohorts. Fibrinoid vessel wall necrosis, haemorrhage and capillaritis were not features of COVID‐19‐related DAD.

Conclusions

DAD is the primary histological manifestation of severe lung disease in COVID‐19 patients who die both in hospital and in the community, suggesting no contribution of hyperoxaemic mechanical ventilation to the histological changes. There are no distinctive morphological features with which to confidently differentiate COVID‐19‐related DAD from DAD due to other causes.

Clinical and Laboratory Diagnosis of SARS-CoV-2, the Virus Causing COVID-19

In December 2019, a novel beta (β) coronavirus eventually named SARS-CoV-2 emerged in Wuhan, Hubei province, China, causing an outbreak of severe and even fatal pneumonia in humans. The virus has spread very rapidly to many countries across the world, resulting in the World Health Organization (WHO) to declare a pandemic on March 11, 2020. Clinically, the diagnosis of this unprecedented illness, called coronavirus disease-2019 (COVID-19), becomes difficult because it shares many symptoms with other respiratory pathogens, including influenza and parainfluenza viruses. Therefore, laboratory diagnosis is crucial for the clinical management of patients and the implementation of disease control strategies to contain SARS-CoV-2 at clinical and population level. Here, we summarize the main clinical and imaging findings of COVID-19 patients and discuss the advances, features, advantages, and limitations of different laboratory methods used for SARS-CoV-2 diagnosis.

Clinical course and findings of 14 patients with COVID-19 compared with 5 patients with conventional human coronavirus pneumonia

OBJECTIVE

To clarify what future problems must be resolved and how clinical findings of SARS-CoV-2 infection differ from those of cHCoV infection.

METHODS

Patients and Methods Clinical characteristics of 14 patients with laboratory-confirmed Coronavirus disease 2019 (COVID-19) and 5 patients with cHCoV pneumonia admitted to our institution and treated up to March 8, 2020, were retrospectively analyzed.

RESULTS

On admission, 10 patients had pneumonia, 5 of whom had pulmonary shadows detectable only via computed tomography (CT). During hospitalization, another patient with no pulmonary shadows on admission developed pneumonia. In total, 11 (78.6%) of the 14 patients developed pneumonia, indicating its high prevalence in COVID-19. During hospitalization, the patients' symptoms spontaneously relapsed and resolved, and gastrointestinal symptoms were frequently found. C-reactive protein values showed correlation with the patients' clinical courses. Ritonavir/lopinavir were administered to 5 patients whose respiratory conditions worsened during admission, all of whom improved. However, the pneumonia in the 6 other patients improved without antivirals. None of the 14 patients died, whereas 5 other patients with cHCoV pneumonia were in respiratory failure on admission, and one patient (20%) died.

CONCLUSION

Both SARS-CoV-2 and cHCoV can cause severe pneumonia. Problems for future resolution include whether antiviral agents administered in cases of mild or moderate severity can reduce the number of severe cases, and whether antivirals administered in severe cases can reduce mortality.

Transfer Learning with Deep Convolutional Neural Network (CNN) for Pneumonia Detection Using Chest X-ray

Pneumonia is a life-threatening disease, which occurs in the lungs caused by either bacterial or viral infection. It can be life-endangering if not acted upon at the right time and thus the early diagnosis of pneumonia is vital. The paper aims to automatically detect bacterial and viral pneumonia using digital x-ray images. It provides a detailed report on advances in accurate detection of pneumonia and then presents the methodology adopted by the authors. Four different pre-trained deep Convolutional Neural Network (CNN): AlexNet, ResNet18, DenseNet201, and SqueezeNet were used for transfer learning. A total of 5247 chest X-ray images consisting of bacterial, viral, and normal chest x-rays images were preprocessed and trained for the transfer learning-based classification task. In this study, the authors have reported three schemes of classifications: normal vs. pneumonia, bacterial vs. viral pneumonia, and normal, bacterial, and viral pneumonia. The classification accuracy of normal and pneumonia images, bacterial and viral pneumonia images, and normal, bacterial, and viral pneumonia were 98%, 95%, and 93.3%, respectively. This is the highest accuracy, in any scheme, of the accuracies reported in the literature. Therefore, the proposed study can be useful in more quickly diagnosing pneumonia by the radiologist and can help in the fast airport screening of pneumonia patients.

Clinical Characteristics and Differential Clinical Diagnosis of Novel Coronavirus Disease 2019 (COVID-19)

Novel Coronavirus Disease (COVID-19) has become a rapidly growing pandemic involving several nations. It is of serious concern and extreme challenge not only to the health personnel but also to the countries for containment. The causative organism is SARS-CoV-2, RNA virus of subgenus Sarbecovirus, similar to the SARS virus, and seventh member of the human coronavirus family responsible for this zoonotic infection. It binds to the human angiotensin converting enzyme (hACE-2) receptor and causes constitutional and respiratory symptoms. The major mode of transmission is human to human and the median incubation period is 4 days. The most common symptom as studied from various cohorts of COVID-19 patients are fever (83–98%) followed by fatigue (70%) and dry cough (59%); gastrointestinal symptoms are relatively uncommon differentiating it from SARS and MERS. Most of the SAR-CoV-2 infection are mild (80%) with a usual recovery period of 2 weeks. COVID-19 commonly affects males in the middle age and elderly age group, with highest case fatality (8–15%) among those aged >80 years. The disease begins with fever, dry cough, fatigue and myalgia progressing to dyspnoea and ARDS over 6 and 8 days post exposure, respectively. Underlying co-morbidities increase mortality in COVID-19. Poor prognostic factors are elderly, co-morbidities, severe lymphopaenia, high CRP and D-dimer >1 μg/L. The overall mortality rate ranges from 1.5 to 3.6%. COVID-19 has to be differentiated from other viral and bacterial pneumonias as they are more common among healthy adults. Despite constant and vigorous efforts by researchers and health agencies, we are far from containment, cure or prevention by vaccine; hence right information and stringent prevention and control measures are the only weapon in the armoury to combat the ongoing infection.

Innate immunity in coronavirus infection

Coronaviruses (CoVs) comprise a polymorphic group of respiratory viruses causing acute inflammatory diseases in domestic and agricultural animals (chicken, pig, buffalo, cat, dog). Until recently, this infection in humans was mainly observed during the autumn-winter period and characterized by a mild, often asymptomatic, course. The situation changed dramatically in 2003, when SARS outbreak caused by pathogenic CoV (SARS-CoV) was recorded in China. A decade later, a new CoV outbreak occurred in the form of the Middle East respiratory syndrome (MERS-CoV), whereas in December 2019, SARS-CoV-2 (COVID-19) cases were recorded, which transformed within the first months of 2020 into the pandemic. In all three cases, CoV disease led to severe bronchopulmonary lesions, varying from dry, debilitating cough to acute respiratory distress syndrome (ARDS). At the same time, multiple changes in innate immunity were noted most often manifested as a pronounced inflammatory reaction in the lower respiratory tract, featured by damaged type II pneumocytes, apoptosis, hyalinization of alveolar membranes, focal or generalized pulmonary edema. Destructive processes in the respiratory tract were accompanied by migration of monocytes/macrophages and granulocyte neutrophils to the inflammatory focus. Such events were accompanied by production of pro-inflammatory cytokines, which magnitude could ascend up to a cytokine storm. SARS-CoV is characterized by symptoms of secondary immunosuppression, manifested by the late onset of interferon production and activation of NLRP3 inflammasomes – the key inflammatory factor. The reason for such reaction may be accounted for by CoV arsenal containing extensive set of structural and non-structural proteins exerting pro-inflammatory and immunosuppressive properties. Delayed IFN production allowed CoV to replicate actively and freely, and when type I IFN synthesis was eventually triggered, its activity was detrimental and accompanied by an aggravated infection course. Thus, SARS can surely be referred to immune-dependent infections with a marked immunopathological component. The purpose of this review was to describe some mechanisms underlying formation of innate immune response to infection caused by pathogenic coronaviruses SARS-CoV, MERS-CoV and SARS-CoV-2 (COVID-19).

Quantitative computed tomography analysis for stratifying the severity of Coronavirus Disease 2019

To examine the feasibility of using a computer tool for stratifying the severity of Coronavirus Disease 2019 (COVID-19) based on computed tomography (CT) images. We retrospectively examined 44 confirmed COVID-19 cases. All cases were evaluated separately by radiologists (visually) and through an in-house computer software. The degree of lesions was visually scored by the radiologist, as follows, for each of the 5 lung lobes: 0, no lesion present; 1, <1/3 involvement; 2, >1/3 and < 2/3 involvement; and 3, >2/3 involvement. Lesion density was assessed based on the proportion of ground-glass opacity (GGO), consolidation and fibrosis of the lesions. The parameters obtained using the computer tool included lung volume (mL), lesion volume (mL), lesion percentage (%), and mean lesion density (HU) of the whole lung, right lung, left lung, and each lobe. The scores obtained by the radiologists and quantitative results generated by the computer software were tested for correlation. A Chi-square test was used to test the consistency of radiologist- and computer-derived lesion percentage in the right/left lung, upper/lower lobe, and each of the 5 lobes. The results showed a strong to moderate correlation between lesion percentage scores obtained by radiologists and the computer software (r ranged from 0.7679 to 0.8373, P < 0.05), and a moderate correlation between the proportion of GGO and mean lesion density (r = −0.5894, P < 0.05), and proportion of consolidation and mean lesion density (r = 0.6282, P < 0.05). Computer-aided quantification showed a statistical significant higher lesion percentage for lower lobes than that assessed by the radiologists (χ² = 8.160, P = 0.004). Our experiments demonstrated that the computer tool could reliably and accurately assess the severity and distribution of pneumonia on CT scans.

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Lesion percentage calculated by computer and radiologist are highly correlated.

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Lesion density quantifiedby computer was correlated with the visually scored proportion of ground glass opacity and consolidation.

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The computer tool could reliably and accurately assess the distribution of pneumonia.

CT Imaging and Differential Diagnosis of COVID-19

Since the beginning of 2020, coronavirus disease 2019 (COVID-19) has spread throughout China. This study explains the findings from lung computed tomography images of some patients with COVID-19 treated in this medical institution and discusses the difference between COVID-19 and other lung diseases.

Two Cases of Primary Human Parainfluenza Virus 1 Pneumonia in Which Bronchoalveolar Lavage Fluid Yielded Human Parainfluenza Virus 1

Two patients, a 76-year-old woman and 66-year-old woman, presented to our hospital with symptoms of lower respiratory tract infection. Both patients showed chest imaging findings of bilateral ground-glass opacities and consolidations. We initially suspected these patients of having influenza-associated pneumonia and cryptogenic organizing pneumonia, respectively, and performed bronchoalveolar lavage, but only human parainfluenza virus-1 infection was detected by multiplex polymerase chain reaction testing. These findings suggest that pneumonia due to human parainfluenza virus-1 should be included in the differential diagnosis of such cases.

Two cases of primary human parechovirus pneumonia in adults

Human parechoviruses (HPeV) are mainly isolated from upper respiratory tract infection and gastroenteritis in children. HPeV has not been screened for in the past studies of community-acquired pneumonia (CAP) in adults, and its association with CAP is unknown. We present two cases that HPeV was detected by multiplex polymerase chain reaction for respiratory viruses using bronchoalveolar lavage fluid and diagnosed as pneumonia caused by HPeV.