Estimating the extent of asymptomatic COVID-19 and its potential for community transmission: Systematic review and meta-analysis

Management of a large outbreak of COVID-19 at a British Army training centre: lessons for the future

INTRODUCTION

The COVID-19 pandemic has posed major challenges for infection control within training centres, both civilian and military. Here we present a narrative review of an outbreak that occurred at the Royal Military Academy Sandhurst (RMAS) in January-March 2021, in the context of the circulating, highly transmissible SARS-CoV-2 variant B.1.1.7.

METHODS

Testing for SARS-CoV-2 was performed using a combination of reverse transcriptase PCR and Lateral Flow Devices (LFDs). Testing and isolation procedures were conducted in line with a pre-established symptom stratification system. Genomic sequencing was performed on 10 sample isolates.

RESULTS

By the end of the outbreak, 185 cases (153 Officer Cadets, 32 permanent staff) had contracted confirmed COVID-19. This represented 15% of the total RMAS population. This resulted in 0 deaths and 0 hospitalisations, but due to necessary isolation procedures did represent an estimated 12 959 person-days of lost training. 9 of 10 (90%) of sequenced isolates had a reportable lineage. All of those reported were found to be the Alpha lineage B.1.1.7.

CONCLUSIONS

We discuss the key lessons learnt from the after-action review by the Incident Management Team. These include the importance of multidisciplinary working, the utility of sync matrices to monitor outbreaks in real time, issues around Officer Cadets reporting symptoms, timing of high-risk training activities, infrastructure and use of LFDs. COVID-19 represents a vital learning opportunity to minimise the impact of potential future pandemics, which may produce considerably higher morbidity and mortality in military populations.

Incidence of asymptomatic COVID-19 positivity in cancer patients and effects on therapy

PURPOSE

The coronavirus disease 2019 (COVID-19) pandemic is posing unprecedented challenges for patient care, especially for cancer patients. This study looks at asymptomatic (AS) COVID-19 positivity in cancer patients and its effects on their care.

METHODS

We conducted a retrospective chart review of AS patients testing positive for COVID-19 upon screening at Fox Chase Cancer Center between January 2020 and September 2020. Relationships between positive tests and demographics, clinical characteristics, and treatment delays were investigated using conditional logistic regression or Mantel-Haenszel tests.

RESULTS

Among 4143 AS patients who underwent COVID-19 testing, 25 (0.6%) were COVID-19 positive (cases) and these were matched to 50 controls. The median age was lower in the cases compared to that of the controls (64 vs 70 years old, p = 0.04). Of the cases, 10 patients (40%) never underwent their planned oncologic intervention [6/10 (60%) did not require the planned intervention once deemed okay to proceed]. Of the controls, only 1 patient (2%) did not undergo the planned intervention. Of these 15 COVID-19 positive patients who underwent the planned intervention, 11 (73.3%) had a delay related to COVID-19, with a mean delay duration of 18 days (range: 0-49, SD: 16.72).

CONCLUSION

Cancer patients had lower incidence of AS COVID-19 than general population. Delays that occur due to AS COVID screening are not very long and serve as a tool to limit spread of virus. Further studies will be important in addressing delays in cancer care and concerns of patient safety as the pandemic continues.

Effectiveness and Medicoeconomic Evaluation of Home Monitoring of Patients With Mild COVID-19: Covidom Cohort Study

BACKGROUND

Covidom was a telemonitoring solution for home monitoring of patients with mild to moderate COVID-19, deployed in March 2020 in the Greater Paris area in France to alleviate the burden on the health care system. The Covidom solution included a free mobile application with daily monitoring questionnaires and a regional control center to quickly handle patient alerts, including dispatching emergency medical services when necessary.

OBJECTIVE

This study aimed to provide an overall evaluation of the Covidom solution 18 months after its inception in terms of effectiveness, safety, and cost.

METHODS

Our primary outcome was to measure effectiveness using the number of handled alerts, response escalation, and patient-reported medical contacts outside of Covidom. Then, we analyzed the safety of Covidom by assessing its ability to detect clinical worsening, defined as hospitalization or death, and the number of patients with clinical worsening without any preceding alert. We evaluated the cost of Covidom and compared the cost of hospitalization for Covidom and non-Covidom patients with mild COVID-19 cases seen in the emergency departments of the largest network of hospitals in the Greater Paris area (Assistance Publique-Hôpitaux de Paris). Finally, we reported on user satisfaction.

RESULTS

Of the 60,073 patients monitored by Covidom, the regional control center handled 285,496 alerts and dispatched emergency medical services 518 times. Of the 13,204 respondents who responded to either of the follow-up questionnaires, 65.8% (n=8690) reported having sought medical care outside the Covidom solution during their monitoring period. Of the 947 patients who experienced clinical worsening while adhering to daily monitoring, only 35 (3.7%) did not previously trigger alerts (35 were hospitalized, including 1 who died). The average cost of Covidom was €54 (US $1=€0.8614) per patient, and the cost of hospitalization for COVID-19 worsening was significantly lower in Covidom than in non-Covidom patients with mild COVID-19 cases seen in the emergency departments of Assistance Publique-Hôpitaux de Paris. The patients who responded to the satisfaction questionnaire had a median rating of 9 (out of 10) for the likelihood of recommending Covidom.

CONCLUSIONS

Covidom may have contributed to alleviating the pressure on the health care system in the initial months of the pandemic, although its impact was lower than anticipated, with a substantial number of patients having consulted outside of Covidom. Covidom seems to be safe for home monitoring of patients with mild to moderate COVID-19.

COVID-19 seroprevalence among local authority workers from Orléans Métropole, the Community of Communes of the Terres du Val de Loire, the local public service management centre of the Loiret department and the Region Centre Val de Loire: a prospective epidemiological study

OBJECTIVE

To evaluate the SARS-CoV-2 seroprevalence among local authority workers, depending on their position and potential interaction with the public.

METHODS

A cohort of volunteer participants was recruited among local authority workers of the Centre Val de Loire region in France, to be tested using a rapid serological test (COVID-PRESTO). The collected data were analysed by comparing different parameters including, gender, age, position held, and contact or not with the public. The study was carried out from August to December 2020 and included 3228 participants (n=3228), from 18 to 65 years old.

RESULTS

The seroprevalence of SARS-CoV-2 among local authority workers was estimated at 3.04%. No significant difference could be observed according to the position held by the workers and whether they were or not in contact with the public. Nevertheless, a significant difference was observed between the different investigating centres, in correlation with the geographical location.

CONCLUSION

Contact with members of the public was not a critical parameter for SARS-CoV-2 seroprevalence as long as protective measures are applied. Among the population included in the study, childcare workers were more at risk of getting infected by the virus.

TRIAL REGISTRATION NUMBER

NCT04387968.

COVID-19: seroprevalence and adherence to preventive measures in Arkhangelsk, Northwest Russia

BACKGROUND

The published estimates of SARS-CoV-2 seroprevalence in Russia are few. The study aimed to assess the SARS-CoV-2 seroprevalence in Arkhangelsk (Northwest Russia), in a year after the start of the pandemic, to evaluate the population adherence to non-pharmaceutical interventions (NPIs), and to investigate characteristics associated with COVID-19 seropositive status.

METHODS

We conducted a SARS-CoV-2 seroprevalence study between 24 February and 30 June 2021 involving 1332 adults aged 40-74 years. Logistic regression models were fit to identify factors associated with seropositive status and with adherence to NPIs.

RESULTS

Less than half (48.9%) of study participants adhered all recommended NPIs. Male sex (odds ratio [OR] 1.7, 95% confidence intervals [CI] 1.3; 2.3), regular employment (OR 1.8, 95% CI 1.3; 2.5) and low confidence in the efficiency of the NPIs (OR 1.9, 95% CI 1.5; 2.5) were associated with low adherence to internationally recommended NPIs. The SARS-CoV-2 seroprevalence rate was 65.1% (95% CI: 62.5; 67.6) and increased to 73.0% (95% CI: 67.1; 85.7) after adjustment for test performance. Regular employment (OR 2.0, 95% CI 1.5; 2.8) and current smoking (OR 0.4, 95% CI 0.2; 0.5) were associated with being seropositive due to the infection.

CONCLUSIONS

Two third of the study population were seropositive in a year after the onset of the pandemic in Arkhangelsk. Individuals with infection-acquired immunity were more likely to have regular work and less likely to be smokers. The adherence to NPIs was not found associated with getting the virus during the first year of the pandemic.

B, Monica MS, Thyago H. C. Incursions by severe acute respiratory syndrome coronavirus-2 on the host anti-viral immunity during mild, moderate, and severe coronavirus disease 2019 disease

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection in the human host can lead to various clinical manifestations, from symptomless carriers to mild to moderate to severe/critical illness. Therefore, the clinical classification of SARS-CoV-2 disease, based on severity, is a reliable way to predict disease states in SARS-CoV-2 infection. Recent studies on genomics, transcriptomics, epigenomics, and immunogenomics, along with spatial analysis of immune cells have delineated and defined the categorization of these disease groups using these high throughout technologies. These technologies hold the promise of providing not only a detailed but a holistic view of SARS-CoV-2-led pathogenesis. The main genomic, cellular, and immunologic features of each disease category, and what separates them spatially and molecularly are discussed in this brief review to provide a foundational spatial understanding of SARS-CoV-2 immunopathogenesis.

Effectiveness of facemasks for opening a university campus in Mississippi, United States - a modelling study

Background: Universities are at risk for COVID-19 and Fall semester begins in August 2020 for most campuses in the United States. The Southern States, including Mississippi, are experiencing a high incidence of COVID-19. Aims: The objective of this study is to model the impact of face masks and hybrid learning on the COVID-19 epidemic on Mississippi State University (MSU) campus. Methods: We used an age structured deterministic mathematical model of COVID-19 transmission within the MSU campus population, accounting for asymptomatic transmission. We modeled facemasks for the campus population at varying proportions of mask use and effectiveness, and Hyflex model of partial online learning with reduction of people on campus. Results: Facemasks can substantially reduce cases and deaths, even with modest effectiveness. Even 20% uptake of masks will halve the epidemic size. Facemasks combined with Hyflex reduces epidemic size even more. Conclusions: Universal use of face masks and reducing the number of people on campus may allow safer universities reopening.

Current global research landscape on COVID-19 and cancer: Bibliometric and visualization analysis

BACKGROUND

Cancer is a severe public health issue that seriously jeopardizes global health. In individuals with coronavirus disease 2019 (COVID-19), cancer is considered an independent risk factor for severe illness and increased mortality.

AIM

To identify research hotspots and prospects, we used bibliometrics to examine the global production of COVID-19 literature published in the field of oncology.

METHODS

Data on publication output were identified based on the Scopus database between January 1, 2020, and June 21, 2022. This study used VOSviewer to analyze collaboration networks among countries and assess the terms most often used in the titles and abstracts of retrieved publications to determine research hotspots linked to cancer and COVID-19. The Impact Index Per Article for the top 10 high-cited papers collected from Reference Citation Analysis (RCA) are presented.

RESULTS

A total of 7015 publications were retrieved from the database. The United States published the greatest number of articles (2025; 28.87%), followed by Italy (964; 13.74%), the United Kingdom (839; 11.96%), and China (538; 7.67%). The University of Texas MD Anderson Cancer Center (n = 205, 2.92%) ranked first, followed by the Memorial Sloan-Kettering Cancer Center (n = 176, 2.51%). The European Journal of Cancer (n = 106, 1.51%) ranked first, followed by the Frontiers in Oncology (n = 104, 1.48%), Cancers (n = 102, 1.45%), and Pediatric Blood and Cancer (n = 95; 1.35%). The hot topics were stratified into “cancer care management during the COVID-19 pandemic”; and “COVID-19 vaccines in cancer patients”.

CONCLUSION

This is the first bibliometric analysis to determine the present state and upcoming hot themes related to cancer and COVID-19 and vice versa using VOSviewer during the early stages of the pandemic. The emergence of hot themes related to cancer and COVID-19 may aid researchers in identifying new research areas in this field.

Biosensors for the detection of disease outbreaks through wastewater-based epidemiology

Wastewater-Based Epidemiology (WBE) is a novel community-wide monitoring tool that provides comprehensive real-time data of the public and environmental health status and can contribute to public health interventions, including those related to infectious disease outbreaks (e.g., the ongoing COVID-19 pandemic). Nonetheless, municipalities without centralized laboratories are likely still not able to process WBE samples. Biosensors are a potentially cost-effective solution to monitor the development of diseases through WBE to prevent local outbreaks. This review discusses the economic and technical feasibility of eighteen recently developed biosensors for the detection and monitoring of infectious disease agents in wastewater, prospecting the prevention of future pandemics.

Humoral and cellular response in convalescent COVID-19 lupus patients

In SLE, underlying immune dysregulation and immunosuppression may increase the susceptibility to COVID-19 and impair the humoral and adaptive response. We aimed to characterize COVID-19 infection, identifying susceptibility and severity risk factors, assessing the presence of SARS-CoV-2 IgG antibodies and analyzing the cellular response. We established a prospective cohort of lupus patients to estimate the COVID-19 incidence compared to the reference general population. Data were collected via telephone interviews and medical record review. SARS-CoV-2 IgG antibodies were measured cross-sectionally as part of routine surveillance. Longitudinal changes in antibody titers and immunological profile from convalescent COVID-19 patients were evaluated at 6, 12 and 24 week after symptom onset. From immunological studies, PBMCs from convalescent patients were extracted and analyzed by flow cytometry and gene expression analysis. We included 725 patients, identifying 29 with PCR-confirmed COVID-19 infection and 16 with COVID-19-like symptoms without PCR-testing. Of the 29 confirmed cases, 7 had severe disease, 8 required hospital admission (27.6%), 4 intensive care, and 1 died. COVID-19 accumulated incidence was higher in lupus patients. Health care workers and anti-SSA/Ro52 antibody positivity were risk factors for COVID-19 susceptibility, and hypocomplementemia for severity. SARS-CoV-2 IgG antibodies were detected in 8.33% of patients. Three fourths of confirmed COVID-19 cases developed antibodies. High prednisone doses were associated with lack of antibody response. Antibody titers declined over time (39%). Convalescent patients at week 12 after symptom onset displayed a CD8⁺T cell reduction and predominant Th17 with a mild Th2 response, more pronounced in severe COVID-19 disease. Longitudinal immune response analysis showed a progressive sustained increase in CD8⁺ T and B memory cells with a decrease of Th17 signaling. Lupus patients are at higher risk of COVID-19 infection and new susceptibility and severity risk factors were identified. Lupus patients were able to mount humoral and cellular responses despite immunosuppressive therapy.

Evaluation of different types of face masks to limit the spread of SARS-CoV-2: a modeling study

We expanded a published mathematical model of SARS-CoV-2 transmission with complex, age-structured transmission and with laboratory-derived source and wearer protection efficacy estimates for a variety of face masks to estimate their impact on COVID-19 incidence and related mortality in the United States. The model was also improved to allow realistic age-structured transmission with a pre-specified R0 of transmission, and to include more compartments and parameters, e.g. for groups such as detected and undetected asymptomatic infectious cases who mask up at different rates. When masks are used at typically-observed population rates of 80% for those ≥ 65 years and 60% for those < 65 years, face masks are associated with 69% (cloth) to 78% (medical procedure mask) reductions in cumulative COVID-19 infections and 82% (cloth) to 87% (medical procedure mask) reductions in related deaths over a 6-month timeline in the model, assuming a basic reproductive number of 2.5. If cloth or medical procedure masks’ source control and wearer protection efficacies are boosted about 30% each to 84% and 60% by cloth over medical procedure masking, fitters, or braces, the COVID-19 basic reproductive number of 2.5 could be reduced to an effective reproductive number ≤ 1.0, and from 6.0 to 2.3 for a variant of concern similar to delta (B.1.617.2). For variants of concern similar to omicron (B.1.1.529) or the sub-lineage BA.2, modeled reductions in effective reproduction number due to similar high quality, high prevalence mask wearing is more modest (to 3.9 and 5.0 from an R₀ = 10.0 and 13.0, respectively). None-the-less, the ratio of incident risk for masked vs. non-masked populations still shows a benefit of wearing masks even with the higher R0 variants.

Monitoring of anti-SARS-CoV-2 IgG antibody immune responses in two cohorts of Hungarian healthcare workers following infection or immunization

Összefoglaló. Bevezetés: A SARS-CoV-2-fertőzések és az anti-SARS-CoV-2-vakcinák által kiváltott immunvédelem tartóssága, nagysága és különbségeinek háttere nem teljesen tisztázott, az oltási protokollok optimális időzítése vitatott. Célkitűzés: A humorális immunválaszok nagyságát, időbeli változását, a reinfekciók gyakoriságát, demográfiai és klinikai paraméterekkel való összefüggését vizsgáltuk magyarországi egészségügyi dolgozóknál. Módszerek: Megyei egyetemi oktató kórházunkban prospektív, longitudinális vizsgálatot végeztünk egészségügyi dolgozók két csoportjában. 1. kohorsz: SARS-CoV-2-fertőzésen átesett, oltatlan 42 dolgozó (nő: 100%) antinukleokapszid-IgG-szintjét mértük 8 hónapon keresztül (2020. június-2021. február). Az immunválasznak a változását és az életkorral, a krónikus betegségekkel, a vércsoporttal és a tünetek súlyosságával való összefüggését vizsgáltuk. 2. kohorsz: két dózis mRNS-vakcinával (Pfizer-BioNTech) végzett immunizálást követően, fertőzésnaiv 49 dolgozó (nő: 73%) anti-spike-RBD-protein-IgG-szintjét monitoroztuk 8 hónapig (2020. december-2021. augusztus). Medián analízis, lineáris regresszió, ANCOVA, Kruskal-Wallis- és Skillings-Mack-teszt-elemzéseket végeztünk. Eredmények: 1. kohorsz: az IgG-szintek átlagosan a betegség 4-es súlyossági kategóriájában voltak a legmagasabbak, a negatív tartományba csökkenés medián ideje 6 hónap volt. 2. kohorsz: a második vakcina hatására az IgG-szint a 25-szörösére nőtt, majd 210 nap után a csúcsszint 6%-ra csökkent. Az ellenanyagtiter negatív összefüggést mutatott az idősebb életkorral és a férfinemmel. Tünetmentes (újra)fertőződést valószínűsítettünk a fertőzésen átesettek 17%-ánál és az immunizált kohorsz 14%-ánál. Az érintettek magas kockázatú osztályokon dolgoztak. Következtetés: 6 hónap után mind a fertőzésen átesettek, mind az immunizáltak jelentősen csökkenő IgG-védelmet mutattak. A (re)infekciók átlagosan 15%-ban, tünetmentesen zajlottak. Az eredmények megerősítik az oltás hatékonyságát a betegség megelőzésében, a harmadik emlékeztető vakcina fontosságát 6 hónap után és az anti-SARS-CoV-2-IgG-monitorozás potenciális értékét. Orv Hetil. 2022; 163(12): 455-462.

SUMMARY

INTRODUCTION

The length, level and variation of immune responses to infection with SARS-CoV-2 or following anti-SARS-CoV-2 vaccination remains unclear, optimal (re)vaccination protocols remain debated.

OBJECTIVE

We investigated the magnitude of humoral immune responses, their over-time changes, the frequency of (re)infections and the association with demographic and clinical parameters in Hungarian healthcare workers.

METHODS

We conducted a prospective, longitudinal study in two groups of healthcare workers of a public, county-level teaching hospital. Cohort 1: The anti-nucleocapsid IgG levels of 42 workers (female: 100%) were followed up over 8 months after SARS-CoV-2 infection (June 2020-February 2021). The change in humoral immune response and its associations with age, existing chronic conditions, blood type and severity of symptoms were investigated. Cohort 2: The anti-spike-RBD protein IgG levels of 49 workers (female: 73%) with no prior COVID-19 infection were monitored over 8 months (December 2020-August 2021) following immunisation with two doses of mRNA vaccine (Pfizer-BioNTech). Analyses included median analysis, linear regression, ANCOVA, Kruskal-Wallis and Skilling-Mack tests.

RESULTS

Cohort 1: IgG levels were on average the highest among those in illness severity category 4, the median time of IgG level reduction below the positive test cut-off was 6 months. Cohort 2: The IgG levels increased 25-fold between the first and second immunisations, but decreased to 6% of the peak level after 210 days. They showed an overall negative association with older age and male sex. The suspected levels of (re)infections were 17% and 14% within the infected and the immunised cohorts, respectively, all symptomless. Those affected all worked on high-risk wards.

CONCLUSION

Both the infected and the immunised cohorts showed significantly declining IgG protections beyond 6 months. The average observed rate of (re)infections was 15%, all asymptomatic. Our findings are confirmative of the effectiveness of vaccination to prevent illness, the importance of booster vaccination due to declining humoral immune protection beyond 6 months, and the potential value of anti-SARS-CoV-2 IgG monitoring. Orv Hetil. 2022; 163(12): 455-462.

Asymptomatic and pre-symptomatic infection in Coronavirus Disease 2019 pandemic

With the presence of Coronavirus Disease 2019 (COVID-19) asymptomatic infections detected, their proportion, transmission potential, and other aspects such as immunity and related emerging challenges have attracted people's attention. We have found that based on high-quality research, asymptomatic infections account for at least one-third of the total cases, whereas based on systematic review and meta-analysis, the proportion is about one-fifth. Evaluating the true transmission potential of asymptomatic cases is difficult but critical, since it may affect national policies in response to COVID-19. We have summarized the current evidence and found, compared with symptomatic cases, the transmission capacity of asymptomatic individuals is weaker, even though they have similar viral load and relatively short virus shedding duration. As the outbreak progresses, asymptomatic infections have also been found to develop long COVID-19. In addition, the role of asymptomatic infection in COVID-19 remains to be further revealed as the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants continue to emerge. Nevertheless, as asymptomatic infections transmit the SARS-CoV-2 virus silently, they still pose a substantial threat to public health. Therefore, it is essential to conduct screening to obtain more knowledge about the asymptomatic infections and to detect them as soon as possible; meanwhile, management of them is also a key point in the fight against COVID-19 community transmission. The different management of asymptomatic infections in various countries are compared and the experience in China is displayed in detail.

Modeling the effect of the vaccination campaign on the COVID-19 pandemic

Population-wide vaccination is critical for containing the SARS-CoV-2 (COVID-19) pandemic when combined with restrictive and prevention measures. In this study we introduce SAIVR, a mathematical model able to forecast the COVID-19 epidemic evolution during the vaccination campaign. SAIVR extends the widely used Susceptible-Infectious-Removed (SIR) model by considering the Asymptomatic (A) and Vaccinated (V) compartments. The model contains several parameters and initial conditions that are estimated by employing a semi-supervised machine learning procedure. After training an unsupervised neural network to solve the SAIVR differential equations, a supervised framework then estimates the optimal conditions and parameters that best fit recent infectious curves of 27 countries. Instructed by these results, we performed an extensive study on the temporal evolution of the pandemic under varying values of roll-out daily rates, vaccine efficacy, and a broad range of societal vaccine hesitancy/denial levels. The concept of herd immunity is questioned by studying future scenarios which involve different vaccination efforts and more infectious COVID-19 variants.

Spectrum of COVID-19 clinical characteristics among patients presenting to the primary healthcare in Qatar during the early stages of the pandemic: a retrospective multicentre cross-sectional study

OBJECTIVES

To describe clinical characteristics and laboratory investigations of patients with COVID-19 diagnosed in primary care in Qatar and to assess predictors of hospitalisation.

DESIGN

A retrospective cross-sectional study.

SETTING AND PARTICIPANTS

3515 confirmed patients with COVID-19 diagnosed in any of the 27 primary healthcare centres in Qatar between 9 April 2020 and 30 June 2020.

MAIN OUTCOME MEASURES

Demographic characteristics, comorbidities, contact tracing, clinical and laboratory data, in addition to patient disposition at the time of diagnosis RESULTS: Mean age of patients was 35.5 years (±14.7). 2285 patients (65.0%) were males, 961 patients (27.3%) had a history of concomitant comorbidity and 640 patients (18.2%) were asymptomatic. Adult patients (19-64 years old) were more likely to report symptoms than children or elderly. Fever and cough were the most frequently documented symptoms affecting 1874 patients (46.7%) and 1318 patients (37.5%), respectively. Most patients had normal vital signs at presentation; however, patients who were subsequently hospitalised had higher median temperature than non-hospitalised patients (37.7°C, IQR: 37.0°C-38.4°C, and 37.2°C, IQR: 36.8°C-37.8°C, respectively). Hospitalised patients had significantly higher C reactive protein (CRP) (median CRP: 20 mg/L, IQR: 5.0-61.2 mg/L) than non-hospitalised patients (median CRP: 4.6 mg/L, IQR: 1.7-11.50 mg/L), and lower median absolute lymphocyte count (1.5×103/µL, IQR: 1.1×103/µL-2.1×103/µL, and 1.8×103/µL, IQR: 1.3×103/µL-2.4×103/µL, respectively). Predictors of hospitalisation were increasing age (adjusted OR (AOR): 2.614, 95% CI 1.281 to 5.332 for age between 50 years and 64 years, and AOR: 3.892, 95% CI 1.646 to 9.204 for age ≥65 years), presence of two or more comorbidities (AOR: 2.628; 95% CI 1.802 to 3.832) and presence of symptoms (AOR: 1.982: 95% CI 1.342 to 2.928).

CONCLUSION

The majority of COVID-19 cases diagnosed in primary healthcare in Qatar were symptomatic. Most cases had normal vital signs and laboratory results at presentation. Predictors of hospitalisation were increasing age, the presence of symptoms and having two or more comorbidities.

Seroprevalence of anti-SARS-CoV-2 antibodies after the first wave of the COVID-19 pandemic in a vulnerable population in France: a cross-sectional study

OBJECTIVES

We aimed to assess the level of prior SARS-CoV-2 infection in socially deprived neighbourhoods after the first wave of the pandemic, and to identify factors associated with seropositivity.

DESIGN

A cross-sectional study.

SETTING

Three socially deprived neighbourhoods of the city of Perpignan, in the south of France, where large settled Roma communities live.

PARTICIPANTS

People aged 6 years old or over, living in the study area. 700 people were included in the study using two-stage stratified sampling design.

INTERVENTIONS

The study included a questionnaire and SARS-CoV-2 antibody testing by the Roche Elecsys immunoassay between 29 June and 17 July 2020.

PRIMARY AND SECONDARY OUTCOME MEASURES

SARS-CoV-2 antibody seroprevalence was estimated from weighted data. Associated factors and reported symptoms were investigated using univariable and multivariable logistic regressions.

RESULTS

The seroprevalence of anti-SARS-CoV-2 antibodies was 35.4% (95% CI 30.2% to 41.0%). People aged 15-64 years old had increased odds of being seropositive than those aged 65 years or over. Obese people had higher odds of being seropositive (adjusted OR (aOR)=2.0, 95% CI 1.1 to 3.8). The odds of being seropositive were higher in households with clinical COVID-19 cases (one case: aOR=2.5, 95% CI 1.3 to 5.0; several cases: aOR=6.9, 95% CI 3.1 to 15.2). In the neighbourhood with the highest measured seroprevalence, people living in a dwelling with one to two rooms had higher odds of being seropositive than those living in a four-room house (aOR=2.8, 95% CI 1.2 to 6.3). Working during the lockdown was associated with lower odds of being seropositive (aOR=0.2, 95% CI 0.03 to 1.0).

CONCLUSION

Transmission of SARS-COV-2 in this vulnerable population was very high during the COVID-19 pandemic's first wave. Our results highlight the need to strengthen and adapt preventive measures taking into account all social determinants of health, especially housing conditions.

Compound hazards: An examination of how hurricane protective actions could increase transmission risk of COVID-19

Hurricane season brings new and complex challenges as we continue to battle the COVID-19 pandemic. In May 2020, the National Oceanic and Atmospheric Administration has predicted nearly twice the normal number of tropical storms and hurricanes this season, while projections of COVID-19 models continue to rise in the United States as the Atlantic hurricane season progresses. Our research examines the critical intersection of hurricane response and public health in Harris County, Texas. We examine a hypothetical case of the 2017 Hurricane Harvey occurring amid the current pandemic. This research uses point of interest visitations as location intelligence data provided by SafeGraph together with Social Vulnerability Index and historical flood data to examine the critical intersection of natural hazard planning and response and the COVID-19 pandemic to assess the risks of a compound hazard situation. COVID-19 transmission hotspots and businesses in a community due to storm preparation activity were identified. The main drivers of transmission risk arise from overall pandemic exposure and increased interpersonal contact during hurricane preparation. Residents of health-risk areas will need to make logistical arrangements to visit alternative medical facilities for treatments related to either COVID-19 or physical impacts, such as injuries, due to the hurricane risks. Points of interest needed for disaster preparation are more likely to be situated in high-risk areas, therefore making cross-community spread more likely. Moreover, greater susceptibility could arise from social vulnerability (socioeconomic status and demographic factors) and disrupted access to healthcare facilities. Results from this study can be used to identify high-risk areas for COVID-19 transmission for prioritization in planning for temporary healthcare centers and other essential services in low-risk areas. Understanding the interplay between disaster preparation and the restrictive environment laid out by the pandemic is critical for community leaders and public health officials for ensuring the population has sufficient access to essential infrastructure services. The findings from this study can help guide the direction of disaster planning and pandemic response strategies and policies.

Modeling the impact of vaccination strategies for nursing homes in the context of increased SARS-CoV-2 community transmission and variants.. [PMID: 34729570 PMCID: PMC8562554 DOI: 10.1101/2021.10.25.21265493]

Nursing homes (NH) were among the first settings to receive COVID-19 vaccines in the United States, but staff vaccination coverage remains low at an average of 64%. Using an agent-based model, we examined the impact of community prevalence, the Delta variant, staff vaccination coverage, and boosters for residents on outbreak dynamics in nursing homes. We found that increased staff primary series coverage and high booster vaccine effectiveness (VE) in residents leads to fewer infections and that the cumulative incidence is highly dependent on community transmission. Despite high VE, high community transmission resulted in continued symptomatic infections in NHs.

Managing passenger flows for seaborne transportation during COVID-19 pandemic

The ongoing coronavirus disease 2019 (COVID-19) pandemic has negatively affected the cruise and ferry industry as the passenger numbers and revenues have plummeted. Therefore, we developed a holistic approach for mitigating COVID-19 during seaborne transportation in a cost-efficient way by combining behavioural changes, procedural workflows and technical innovations to reset the industry.

The use of face masks during vaccine roll-out in New YorkCity and impact on epidemic control

Face masks were mandated in New York during the first wave in 2020, and in 2021 the first vaccine programs have commenced. We aimed to examine the impact of face mask and other NPIs use with a gradual roll out of vaccines in NYC on the epidemic trajectory.

A SEIR mathematical model of SARS-CoV-2 transmission was developed for New York City (NYC), which accounted for decreased mobility for lockdown, testing and tracing. Varied mask’s usage and efficacy were tested, along with a gradual increase in vaccine uptake over five months. The model has been calibrated using notification data in NYC from March first to June 29.

Masks and other NPIs result in immediate impact on the epidemic, while vaccination has a delayed impact, especially when implemented over a long period of time. A pre-emptive, early mandate for masks is more effective than late mask use, but even late mask mandates will reduce cases and deaths by over 20%. The epidemic curve is suppressed by at least 50% of people wearing a mask from the start of the outbreak but surges when mask wearing drops to 30% or less. With a slow roll out of vaccines over five months at uptake levels of 20–70%, NPIs use will still be needed and has a greater impact on epidemic control.

When vaccine roll out is slow or partial in cities experiencing local transmission of COVID-19, masks and other NPIs will be necessary to mitigate transmission until vaccine coverage is high and complete. Vaccine alone cannot rapidly control an epidemic because of the time lag to two-dose immunity. Even after high coverage, the ongoing need for NPIs is unknown and will depend on long-term duration of vaccine efficacy, the use of boosters and optimized dosage scheduling and variants of concern.

SARS-CoV-2 infection in patients with primary central nervous system lymphoma

BACKGROUND

Cancer patients may be at higher risk for severe coronavirus infectious disease-19 (COVID-19); however, the outcome of Primary Central Nervous System Lymphoma (PCNSL) patients with SARS-CoV-2 infection has not been described yet.

METHODS

We conducted a retrospective study within the Lymphomes Oculo-Cérébraux national network (LOC) to assess the clinical characteristics and outcome of SARS-CoV-2 infection in PCNSL patients (positive real-time polymerase chain reaction of nasopharyngeal swab or evocative lung computed tomography scan). We compared clinical characteristics between patients with severe (death and/or intensive care unit admission) and mild disease.

RESULTS

Between March and May 2020, 13 PCNSL patients were diagnosed with SARS-CoV-2 infection, 11 (85%) of whom were undergoing chemotherapy at the time of infection. The mortality rate was 23% (3/13), and two additional patients (15%) required mechanical ventilation. Two patients (15%) had no COVID-19 symptoms. History of diabetes mellitus was more common in severe patients (3/5 vs 0/8, p = 0.03). Two patients recovered from COVID-19 after mechanical ventilation during more than two weeks and resumed chemotherapy. In all, chemotherapy was resumed after COVID-19 recovery in nine patients (69%) after a median delay of 16 days (range 3-32), none of whom developed unusual chemotherapy complication nor SARS-Cov2 reactivation.

CONCLUSION

This preliminary analysis suggests that, while being at higher risk be for severe illness, PCNSL patients with COVID-19 might be treated maximally especially if they achieved oncological response at the time of SARS-CoV-2 infection. Chemotherapy might be resumed without prolonged delay in PCNSL patients with COVID-19.

Efficacy of compartmentalization in controlling an adenovirus type 54 keratoconjunctivitis outbreak on Oki Island, Japan

PURPOSE

To analyze the epidemiologic characteristics of an outbreak of human adenovirus type 54 (HAdV-54) on Oki Island, Shimane Prefecture, Japan, in 2017 and to assess the effectiveness of a compartmentalization method in controlling the incidence and spread.

STUDY DESIGN

Retrospective cohort study.

METHODS

The infection was diagnosed in 136 individuals, and typing was confirmed by PCR and direct sequencing. The epidemiologic characteristics of the disease including the infection rate, incubation period, and basic reproductive number (R0), ie, number of cases directly infected by an infectious patient during the course of the disease, were investigated. The effectiveness of compartmentalization for infection control was determined by simulating the outbreak using the Susceptible-Exposed-Infectious-Recovered (SEIR) model.

RESULTS

The majority of the HAdV-54-infected individuals were the children of 3 nursery schools (A, B, and C) and their parents on Oki Island. The infection rates in the 3 schools were 13.2%, 16.9%, and 17.2%, respectively. The one class of school B without the index case was initially compartmentalized, and the infection rate in this compartment was 0%. The incubation period was calculated to be 9.3 ± 3.5 days, and the disease duration, 13.0 ± 5.4 days. The R0 was 1.43. Using these parameters, a SEIR model was constructed. The SEIR model well predicted the daily incidence of infection and indicated that the compartmentalization method provides effective reduction in the incidence of the infection, with much earlier control.

CONCLUSIONS

The compartmentalization method is effective to control HAdV-54 outbreaks.

SARS-CoV-2 Seroprevalence Among Healthcare Workers by Workplace Exposure Risk in Kashmir, India

BACKGROUND

SARS-CoV-2 infection (COVID-19) poses a tremendous challenge to healthcare systems across the globe. Serologic testing for SARS-CoV-2 infection in healthcare workers (HCWs) may quantify the rate of clinically significant exposure in an institutional setting and identify those HCWs who are at greatest risk.

METHODS

We conducted a survey and SARS-CoV-2 serologic testing among a convenience sample of HCWs from 79 non-COVID and 3 dedicated COVID hospitals in District Srinagar of Kashmir, India. In addition to testing for the presence of SARS-CoV-2-specific immunoglobulin G (IgG), we collected information on demographics, occupational group, influenza-like illness (ILI) symptoms, nasopharyngeal reverse transcription polymerase chain reaction (RT-PCR) testing status, history of close unprotected contacts, and quarantine/travel history.

RESULTS

Of 7,346 eligible HCWs, 2,915 (39.7%) participated in the study. The overall prevalence of SARS-CoV-2-specific IgG antibodies was 2.5% (95% CI, 2.0%-3.1%), while HCWs who had ever worked at a dedicated COVID-19 hospital had a substantially lower seroprevalence of 0.6% (95% CI, 0.2%-1.9%). Higher seroprevalence rates were observed among HCWs who reported a recent ILI (12.2%), a positive RT-PCR (27.6%), a history of being put under quarantine (4.9%), and a history of close unprotected contact with a person with COVID-19 (4.4%). Healthcare workers who ever worked at a dedicated COVID-19 hospital had a lower multivariate-adjusted risk of seropositivity (odds ratio, 0.21; 95% CI, 0.06-0.66).

CONCLUSIONS

Our investigation suggests that infection-control practices, including a compliance-maximizing buddy system, are valuable and effective in preventing infection within a high-risk clinical setting. Universal masking, mandatory testing of patients, and residential dormitories for HCWs at COVID-19-dedicated hospitals is an effective multifaceted approach to infection control. Moreover, given that many infections among HCWs are community-acquired, it is likely that the vigilant practices in these hospitals will have spillover effects, creating ingrained behaviors that will continue outside the hospital setting.

Risk Factors of Covid-19 Confirmed Died Patients in Dr. Kariadi Hospital: A Retrospective Study

Covid-19 is a communicable disease causing global pandemic. Some factors inflict worse infection. This study aims to investigate risk factors of Covid-19 confirmed died patients at Dr. Kariadi Hospital Semarang. It is a retrospective study with a total sample of all Covid-19 confirmed patients involving died and healed patients from March to June 2020. Data was gathered from screening forms and analysed with Chi Square (confidence interval of 95%). This study found sixteen risk factors of Covid-19 confirmed died patients involving age (p= 0.000; OR= 8.803; 95% CI 3.982-19.462), entrepreneur (p= 0.041; OR= 14.894; 95% CI 1.12-198.65), farmer/trader (p= 0.029; OR= 25.625; 95% CI 1.40-469.25), contact history (p= 0.000; OR= 12.923; 95% CI 6.163-27.097), fever (p= 0.000; OR= 4.877; 95% CI 2.647-8.984), dyspnea (p=0.000; OR= 17.018; 95% CI 8.523-33.977), cough (p= 0.009; OR= 2.178; 95% CI 1.205-3.935), lethargic (p=0.010; OR= 2.282; 95% CI 1.205-4.323), cold (p= 0.002; OR= 0.180; 95% CI 0.054-0.600), diabetes (p=0.000; OR= 9.767; 95% CI 3.932-24.263), COPD (p= 0.001; OR= 6.360; 95% CI 2.164-18.690), hypertension (p= 0.043; OR= 2.436; 95% CI 1.008-5.887), cancer (p=0.001; OR= 9.647; 95% CI 2.413-38.579), heart disease (p= 0.000; OR= 12.226; 95% CI 2.4-62.294), neurological disorders (p=0.008; OR= 6.057; 95% CI 1.650-22.232), and immune disorders (p=0.031; OR= 1.625; 95% CI 1.186-113.899). Adequate handling is needed to prevent death. in patients with confirmed Covid-19 who have risk factors.

SARS-CoV-2 transmission via aquatic food animal species or their products: A review

Outbreaks of COVID-19 (coronavirus disease 2019) have been reported in workers in fish farms and fish processing plants arising from person-to-person transmission, raising concerns about aquatic animal food products' safety. A better understanding of such incidents is important for the aquaculture industry's sustainability, particularly with the global trade in fresh and frozen aquatic animal food products where contaminating virus could survive for some time. Despite a plethora of COVID-19-related scientific publications, there is a lack of reports on the risk of contact with aquatic food animal species or their products. This review aimed to examine the potential for Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2) contamination and the potential transmission via aquatic food animals or their products and wastewater effluents. The extracellular viability of SARS-CoV-2 and how the virus is spread are reviewed, supporting the understanding that contaminated cold-chain food sources may introduce SAR-CoV-2 via food imports although the virus is unlikely to infect humans through consumption of aquatic food animals or their products or drinking water; i.e., SARS-CoV-2 is not a foodborne virus and should not be managed as such but instead through strong, multifaceted public health interventions including physical distancing, rapid contact tracing, and testing, enhanced hand and respiratory hygiene, frequent disinfection of high-touch surfaces, isolation of infected workers and their contacts, as well as enhanced screening protocols for international seafood trade.

International travel-related control measures to contain the COVID-19 pandemic: a rapid review

BACKGROUND

In late 2019, the first cases of coronavirus disease 2019 (COVID-19) were reported in Wuhan, China, followed by a worldwide spread. Numerous countries have implemented control measures related to international travel, including border closures, travel restrictions, screening at borders, and quarantine of travellers.

OBJECTIVES

To assess the effectiveness of international travel-related control measures during the COVID-19 pandemic on infectious disease transmission and screening-related outcomes.

SEARCH METHODS

We searched MEDLINE, Embase and COVID-19-specific databases, including the Cochrane COVID-19 Study Register and the WHO Global Database on COVID-19 Research to 13 November 2020.

SELECTION CRITERIA

We considered experimental, quasi-experimental, observational and modelling studies assessing the effects of travel-related control measures affecting human travel across international borders during the COVID-19 pandemic. In the original review, we also considered evidence on severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS). In this version we decided to focus on COVID-19 evidence only. Primary outcome categories were (i) cases avoided, (ii) cases detected, and (iii) a shift in epidemic development. Secondary outcomes were other infectious disease transmission outcomes, healthcare utilisation, resource requirements and adverse effects if identified in studies assessing at least one primary outcome.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened titles and abstracts and subsequently full texts. For studies included in the analysis, one review author extracted data and appraised the study. At least one additional review author checked for correctness of data. To assess the risk of bias and quality of included studies, we used the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool for observational studies concerned with screening, and a bespoke tool for modelling studies. We synthesised findings narratively. One review author assessed the certainty of evidence with GRADE, and several review authors discussed these GRADE judgements.

MAIN RESULTS

Overall, we included 62 unique studies in the analysis; 49 were modelling studies and 13 were observational studies. Studies covered a variety of settings and levels of community transmission. Most studies compared travel-related control measures against a counterfactual scenario in which the measure was not implemented. However, some modelling studies described additional comparator scenarios, such as different levels of stringency of the measures (including relaxation of restrictions), or a combination of measures. Concerns with the quality of modelling studies related to potentially inappropriate assumptions about the structure and input parameters, and an inadequate assessment of model uncertainty. Concerns with risk of bias in observational studies related to the selection of travellers and the reference test, and unclear reporting of certain methodological aspects. Below we outline the results for each intervention category by illustrating the findings from selected outcomes. Travel restrictions reducing or stopping cross-border travel (31 modelling studies) The studies assessed cases avoided and shift in epidemic development. We found very low-certainty evidence for a reduction in COVID-19 cases in the community (13 studies) and cases exported or imported (9 studies). Most studies reported positive effects, with effect sizes varying widely; only a few studies showed no effect. There was very low-certainty evidence that cross-border travel controls can slow the spread of COVID-19. Most studies predicted positive effects, however, results from individual studies varied from a delay of less than one day to a delay of 85 days; very few studies predicted no effect of the measure. Screening at borders (13 modelling studies; 13 observational studies) Screening measures covered symptom/exposure-based screening or test-based screening (commonly specifying polymerase chain reaction (PCR) testing), or both, before departure or upon or within a few days of arrival. Studies assessed cases avoided, shift in epidemic development and cases detected. Studies generally predicted or observed some benefit from screening at borders, however these varied widely. For symptom/exposure-based screening, one modelling study reported that global implementation of screening measures would reduce the number of cases exported per day from another country by 82% (95% confidence interval (CI) 72% to 95%) (moderate-certainty evidence). Four modelling studies predicted delays in epidemic development, although there was wide variation in the results between the studies (very low-certainty evidence). Four modelling studies predicted that the proportion of cases detected would range from 1% to 53% (very low-certainty evidence). Nine observational studies observed the detected proportion to range from 0% to 100% (very low-certainty evidence), although all but one study observed this proportion to be less than 54%. For test-based screening, one modelling study provided very low-certainty evidence for the number of cases avoided. It reported that testing travellers reduced imported or exported cases as well as secondary cases. Five observational studies observed that the proportion of cases detected varied from 58% to 90% (very low-certainty evidence). Quarantine (12 modelling studies) The studies assessed cases avoided, shift in epidemic development and cases detected. All studies suggested some benefit of quarantine, however the magnitude of the effect ranged from small to large across the different outcomes (very low- to low-certainty evidence). Three modelling studies predicted that the reduction in the number of cases in the community ranged from 450 to over 64,000 fewer cases (very low-certainty evidence). The variation in effect was possibly related to the duration of quarantine and compliance. Quarantine and screening at borders (7 modelling studies; 4 observational studies) The studies assessed shift in epidemic development and cases detected. Most studies predicted positive effects for the combined measures with varying magnitudes (very low- to low-certainty evidence). Four observational studies observed that the proportion of cases detected for quarantine and screening at borders ranged from 68% to 92% (low-certainty evidence). The variation may depend on how the measures were combined, including the length of the quarantine period and days when the test was conducted in quarantine.

AUTHORS' CONCLUSIONS

With much of the evidence derived from modelling studies, notably for travel restrictions reducing or stopping cross-border travel and quarantine of travellers, there is a lack of 'real-world' evidence. The certainty of the evidence for most travel-related control measures and outcomes is very low and the true effects are likely to be substantially different from those reported here. Broadly, travel restrictions may limit the spread of disease across national borders. Symptom/exposure-based screening measures at borders on their own are likely not effective; PCR testing at borders as a screening measure likely detects more cases than symptom/exposure-based screening at borders, although if performed only upon arrival this will likely also miss a meaningful proportion of cases. Quarantine, based on a sufficiently long quarantine period and high compliance is likely to largely avoid further transmission from travellers. Combining quarantine with PCR testing at borders will likely improve effectiveness. Many studies suggest that effects depend on factors, such as levels of community transmission, travel volumes and duration, other public health measures in place, and the exact specification and timing of the measure. Future research should be better reported, employ a range of designs beyond modelling and assess potential benefits and harms of the travel-related control measures from a societal perspective.

Divergences on expected pneumonia cases during the COVID-19 epidemic in Catalonia: a time-series analysis of primary care electronic health records covering about 6 million people

BACKGROUND

Pneumonia is one of the complications of COVID-19. Primary care electronic health records (EHR) have shown the utility as a surveillance system. We therefore analyse the trends of pneumonia during two waves of COVID-19 pandemic in order to use it as a clinical surveillance system and an early indicator of severity.

METHODS

Time series analysis of pneumonia cases, from January 2014 to December 2020. We collected pneumonia diagnoses from primary care EHR, a software system covering > 6 million people in Catalonia (Spain). We compared the trend of pneumonia in the season 2019-2020 with that in the previous years. We estimated the expected pneumonia cases with data from 2014 to 2018 using a time series regression adjusted by seasonality and influenza epidemics.

RESULTS

Between 4 March and 5 May 2020, 11,704 excess pneumonia cases (95% CI: 9909 to 13,498) were identified. Previously, we identified an excess from January to March 2020 in the population older than 15 years of 20%. We observed another excess pneumonia period from 22 october to 15 november of 1377 excess cases (95% CI: 665 to 2089). In contrast, we observed two great periods with reductions of pneumonia cases in children, accounting for 131 days and 3534 less pneumonia cases (95% CI, 1005 to 6064) from March to July; and 54 days and 1960 less pneumonia cases (95% CI 917 to 3002) from October to December.

CONCLUSIONS

Diagnoses of pneumonia from the EHR could be used as an early and low cost surveillance system to monitor the spread of COVID-19.

Mathematical modeling to inform vaccination strategies and testing approaches for COVID-19 in nursing homes

BACKGROUND

Nursing home residents and staff were included in the first phase of COVID-19 vaccination in the United States. Because the primary trial endpoint was vaccine efficacy (VE) against symptomatic disease, there are limited data on the extent to which vaccines protect against SARS-CoV-2 infection and the ability to infect others (infectiousness). Assumptions about VE against infection and infectiousness have implications for possible changes to infection prevention guidance for vaccinated populations, including testing strategies.

METHODS

We use a stochastic agent-based SEIR model of a nursing home to simulate SARS-CoV-2 transmission. We model three scenarios, varying VE against infection, infectiousness, and symptoms, to understand the expected impact of vaccination in nursing homes, increasing staff vaccination coverage, and different screening testing strategies under each scenario.

RESULTS

Increasing vaccination coverage in staff decreases total symptomatic cases in each scenario. When there is low VE against infection and infectiousness, increasing staff coverage reduces symptomatic cases among residents. If vaccination only protects against symptoms, but asymptomatic cases remain infectious, increased staff coverage increases symptomatic cases among residents through exposure to asymptomatic but infected staff. High frequency testing is needed to reduce total symptomatic cases if the vaccine has low efficacy against infection and infectiousness, or only protects against symptoms.

CONCLUSIONS

Encouraging staff vaccination is not only important for protecting staff, but might also reduce symptomatic cases in residents if a vaccine confers at least some protection against infection or infectiousness.

SUMMARY

The extent of efficacy of SARS-CoV-2 vaccines against infection, infectiousness, or disease, impacts strategies for vaccination and testing in nursing homes. If vaccines confer some protection against infection or infectiousness, encouraging vaccination in staff may reduce symptomatic cases in residents.

COVID-19 basics and vaccine development with a Canadian perspective

The ongoing coronavirus disease 2019 (COVID-19) pandemic is a rapidly evolving situation. New discoveries about COVID-19 and its causative virus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), continue to deepen the understanding of this novel disease. As there is currently no COVID-19 specific treatment, isolation is the most effective method to prevent transmission. Moreover, development of a safe and effective COVID-19 vaccine will be instrumental in reinstating pre-COVID-19 conditions. As of 31 July 2020, there are at least 139 vaccine candidates from around the globe in preclinical evaluation, with another 26 undergoing clinical evaluation. This paper aims to review the basics of COVID-19, including epidemiology, basic biology of SARS-CoV-2, and transmission. We also review COVID-19 vaccine development, including animal models, platforms under development, and vaccine development in Canada.

High-throughput sequencing of SARS-CoV-2 in wastewater provides insights into circulating variants

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged from a zoonotic spill-over event and has led to a global pandemic. The public health response has been predominantly informed by surveillance of symptomatic individuals and contact tracing, with quarantine, and other preventive measures have then been applied to mitigate further spread. Non-traditional methods of surveillance such as genomic epidemiology and wastewater-based epidemiology (WBE) have also been leveraged during this pandemic. Genomic epidemiology uses high-throughput sequencing of SARS-CoV-2 genomes to inform local and international transmission events, as well as the diversity of circulating variants. WBE uses wastewater to analyse community spread, as it is known that SARS-CoV-2 is shed through bodily excretions. Since both symptomatic and asymptomatic individuals contribute to wastewater inputs, we hypothesized that the resultant pooled sample of population-wide excreta can provide a more comprehensive picture of SARS-CoV-2 genomic diversity circulating in a community than clinical testing and sequencing alone. In this study, we analysed 91 wastewater samples from 11 states in the USA, where the majority of samples represent Maricopa County, Arizona (USA). With the objective of assessing the viral diversity at a population scale, we undertook a single-nucleotide variant (SNV) analysis on data from 52 samples with >90% SARS-CoV-2 genome coverage of sequence reads, and compared these SNVs with those detected in genomes sequenced from clinical patients. We identified 7973 SNVs, of which 5680 were novel SNVs that had not yet been identified in the global clinical-derived data as of 17th June 2020 (the day after our last wastewater sampling date). However, between 17th of June 2020 and 20th November 2020, almost half of the SNVs have since been detected in clinical-derived data. Using the combination of SNVs present in each sample, we identified the more probable lineages present in that sample and compared them to lineages observed in North America prior to our sampling dates. The wastewater-derived SARS-CoV-2 sequence data indicates there were more lineages circulating across the sampled communities than represented in the clinical-derived data. Principal coordinate analyses identified patterns in population structure based on genetic variation within the sequenced samples, with clear trends associated with increased diversity likely due to a higher number of infected individuals relative to the sampling dates. We demonstrate that genetic correlation analysis combined with SNVs analysis using wastewater sampling can provide a comprehensive snapshot of the SARS-CoV-2 genetic population structure circulating within a community, which might not be observed if relying solely on clinical cases.

Transmissibility and transmission of respiratory viruses

Human respiratory virus infections lead to a spectrum of respiratory symptoms and disease severity, contributing to substantial morbidity, mortality and economic losses worldwide, as seen in the COVID-19 pandemic. Belonging to diverse families, respiratory viruses differ in how easy they spread (transmissibility) and the mechanism (modes) of transmission. Transmissibility as estimated by the basic reproduction number (R₀) or secondary attack rate is heterogeneous for the same virus. Respiratory viruses can be transmitted via four major modes of transmission: direct (physical) contact, indirect contact (fomite), (large) droplets and (fine) aerosols. We know little about the relative contribution of each mode to the transmission of a particular virus in different settings, and how its variation affects transmissibility and transmission dynamics. Discussion on the particle size threshold between droplets and aerosols and the importance of aerosol transmission for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and influenza virus is ongoing. Mechanistic evidence supports the efficacies of non-pharmaceutical interventions with regard to virus reduction; however, more data are needed on their effectiveness in reducing transmission. Understanding the relative contribution of different modes to transmission is crucial to inform the effectiveness of non-pharmaceutical interventions in the population. Intervening against multiple modes of transmission should be more effective than acting on a single mode.

Seroprevalence of anti-SARS-CoV-2 IgG antibodies in Kenyan blood donors

The spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Africa is poorly described. The first case of SARS-CoV-2 in Kenya was reported on 12 March 2020, and an overwhelming number of cases and deaths were expected, but by 31 July 2020, there were only 20,636 cases and 341 deaths. However, the extent of SARS-CoV-2 exposure in the community remains unknown. We determined the prevalence of anti-SARS-CoV-2 immunoglobulin G among blood donors in Kenya in April-June 2020. Crude seroprevalence was 5.6% (174 of 3098). Population-weighted, test-performance-adjusted national seroprevalence was 4.3% (95% confidence interval, 2.9 to 5.8%) and was highest in urban counties Mombasa (8.0%), Nairobi (7.3%), and Kisumu (5.5%). SARS-CoV-2 exposure is more extensive than indicated by case-based surveillance, and these results will help guide the pandemic response in Kenya and across Africa.

The Anxiety-Buffer Hypothesis in the Time of COVID-19: When Self-Esteem Protects From the Impact of Loneliness and Fear on Anxiety and Depression

INTRODUCTION

The coronavirus (COVID-19) disease has spread worldwide, generating intense fear of infection and death that may lead to enduring anxiety. At the same time, quarantine and physical isolation can intensify feelings of dispositional loneliness that, by focusing on thoughts of disconnection from others, can trigger intense anxiety. Anxiety, generated by both fear of COVID-19 and dispositional loneliness, can activate negative expectations and thoughts of death, potentially generating alarming depressive symptoms. However, the anxiety-buffer hypothesis suggests that self-esteem acts as a shield (buffer) against mental health threats - fear and loneliness - thus hampering anxiety and depressive symptoms.

OBJECTIVE

This study aims to test the process - triggered by COVID-19 fear and loneliness - in which self-esteem should buffer the path leading to anxiety symptoms, then to depression.

METHODS

An observational research design with structural equation models was used. A sample of 1200 participants enrolled from the general population answered an online survey comprising: the fear of COVID-19 scale, the UCLA loneliness scale, the Rosenberg self-esteem scale, and the anxiety and depression scales of the Symptom Checklist-90-Revised.

RESULTS

Structural equation models showed the link between anxiety symptoms (mediator) with both the fear of COVID-19 and dispositional loneliness (predictors), as well as its association with consequent depressive symptomatology (outcome). In line with the anxiety-buffer hypothesis, self-esteem mediated the relationship between the predictors and their adverse psychological consequences.

CONCLUSION

Self-esteem represents a protective factor from the antecedents of depression. Targeted psychological interventions should be implemented to minimize the psychological burden of the disease whilst promoting adaptation and positive psychological health outcomes.

Travel-related control measures to contain the COVID-19 pandemic: a rapid review

BACKGROUND

In late 2019, first cases of coronavirus disease 2019, or COVID-19, caused by the novel coronavirus SARS-CoV-2, were reported in Wuhan, China. Subsequently COVID-19 spread rapidly around the world. To contain the ensuing pandemic, numerous countries have implemented control measures related to international travel, including border closures, partial travel restrictions, entry or exit screening, and quarantine of travellers.

OBJECTIVES

To assess the effectiveness of travel-related control measures during the COVID-19 pandemic on infectious disease and screening-related outcomes.

SEARCH METHODS

We searched MEDLINE, Embase and COVID-19-specific databases, including the WHO Global Database on COVID-19 Research, the Cochrane COVID-19 Study Register, and the CDC COVID-19 Research Database on 26 June 2020. We also conducted backward-citation searches with existing reviews.

SELECTION CRITERIA

We considered experimental, quasi-experimental, observational and modelling studies assessing the effects of travel-related control measures affecting human travel across national borders during the COVID-19 pandemic. We also included studies concerned with severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) as indirect evidence. Primary outcomes were cases avoided, cases detected and a shift in epidemic development due to the measures. Secondary outcomes were other infectious disease transmission outcomes, healthcare utilisation, resource requirements and adverse effects if identified in studies assessing at least one primary outcome.

DATA COLLECTION AND ANALYSIS

One review author screened titles and abstracts; all excluded abstracts were screened in duplicate. Two review authors independently screened full texts. One review author extracted data, assessed risk of bias and appraised study quality. At least one additional review author checked for correctness of all data reported in the 'Risk of bias' assessment, quality appraisal and data synthesis. For assessing the risk of bias and quality of included studies, we used the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool for observational studies concerned with screening, ROBINS-I for observational ecological studies and a bespoke tool for modelling studies. We synthesised findings narratively. One review author assessed certainty of evidence with GRADE, and the review author team discussed ratings.

MAIN RESULTS

We included 40 records reporting on 36 unique studies. We found 17 modelling studies, 7 observational screening studies and one observational ecological study on COVID-19, four modelling and six observational studies on SARS, and one modelling study on SARS and MERS, covering a variety of settings and epidemic stages. Most studies compared travel-related control measures against a counterfactual scenario in which the intervention measure was not implemented. However, some modelling studies described additional comparator scenarios, such as different levels of travel restrictions, or a combination of measures. There were concerns with the quality of many modelling studies and the risk of bias of observational studies. Many modelling studies used potentially inappropriate assumptions about the structure and input parameters of models, and failed to adequately assess uncertainty. Concerns with observational screening studies commonly related to the reference test and the flow of the screening process. Studies on COVID-19 Travel restrictions reducing cross-border travel Eleven studies employed models to simulate a reduction in travel volume; one observational ecological study assessed travel restrictions in response to the COVID-19 pandemic. Very low-certainty evidence from modelling studies suggests that when implemented at the beginning of the outbreak, cross-border travel restrictions may lead to a reduction in the number of new cases of between 26% to 90% (4 studies), the number of deaths (1 study), the time to outbreak of between 2 and 26 days (2 studies), the risk of outbreak of between 1% to 37% (2 studies), and the effective reproduction number (1 modelling and 1 observational ecological study). Low-certainty evidence from modelling studies suggests a reduction in the number of imported or exported cases of between 70% to 81% (5 studies), and in the growth acceleration of epidemic progression (1 study). Screening at borders with or without quarantine Evidence from three modelling studies of entry and exit symptom screening without quarantine suggests delays in the time to outbreak of between 1 to 183 days (very low-certainty evidence) and a detection rate of infected travellers of between 10% to 53% (low-certainty evidence). Six observational studies of entry and exit screening were conducted in specific settings such as evacuation flights and cruise ship outbreaks. Screening approaches varied but followed a similar structure, involving symptom screening of all individuals at departure or upon arrival, followed by quarantine, and different procedures for observation and PCR testing over a period of at least 14 days. The proportion of cases detected ranged from 0% to 91% (depending on the screening approach), and the positive predictive value ranged from 0% to 100% (very low-certainty evidence). The outcomes, however, should be interpreted in relation to both the screening approach used and the prevalence of infection among the travellers screened; for example, symptom-based screening alone generally performed worse than a combination of symptom-based and PCR screening with subsequent observation during quarantine. Quarantine of travellers Evidence from one modelling study simulating a 14-day quarantine suggests a reduction in the number of cases seeded by imported cases; larger reductions were seen with increasing levels of quarantine compliance ranging from 277 to 19 cases with rates of compliance modelled between 70% to 100% (very low-certainty evidence).

AUTHORS' CONCLUSIONS

With much of the evidence deriving from modelling studies, notably for travel restrictions reducing cross-border travel and quarantine of travellers, there is a lack of 'real-life' evidence for many of these measures. The certainty of the evidence for most travel-related control measures is very low and the true effects may be substantially different from those reported here. Nevertheless, some travel-related control measures during the COVID-19 pandemic may have a positive impact on infectious disease outcomes. Broadly, travel restrictions may limit the spread of disease across national borders. Entry and exit symptom screening measures on their own are not likely to be effective in detecting a meaningful proportion of cases to prevent seeding new cases within the protected region; combined with subsequent quarantine, observation and PCR testing, the effectiveness is likely to improve. There was insufficient evidence to draw firm conclusions about the effectiveness of travel-related quarantine on its own. Some of the included studies suggest that effects are likely to depend on factors such as the stage of the epidemic, the interconnectedness of countries, local measures undertaken to contain community transmission, and the extent of implementation and adherence.

Seasonality of Respiratory Viral Infections: Will COVID-19 Follow Suit?

Respiratory viruses, including coronaviruses, are known to have a high incidence of infection during winter, especially in temperate regions. Dry and cold conditions during winter are the major drivers for increased respiratory tract infections as they increase virus stability and transmission and weaken the host immune system. The novel severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) emerged in China in December 2020 and swiftly spread across the globe causing substantial health and economic burdens. Several countries are battling with the second wave of the virus after a devastating first wave of spread, while some are still in the midst of their first wave. It remains unclear whether SARS-CoV-2 will eventually become seasonal or will continue to circulate year-round. In an attempt to address this question, we review the current knowledge regarding the seasonality of respiratory viruses including coronaviruses and the viral and host factors that govern their seasonal pattern. Moreover, we discuss the properties of SARS-CoV-2 and the potential impact of meteorological factors on its spread.

Occurrence and transmission potential of asymptomatic and presymptomatic SARS-CoV-2 infections: A living systematic review and meta-analysis

BACKGROUND

There is disagreement about the level of asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We conducted a living systematic review and meta-analysis to address three questions: (1) Amongst people who become infected with SARS-CoV-2, what proportion does not experience symptoms at all during their infection? (2) Amongst people with SARS-CoV-2 infection who are asymptomatic when diagnosed, what proportion will develop symptoms later? (3) What proportion of SARS-CoV-2 transmission is accounted for by people who are either asymptomatic throughout infection or presymptomatic?

METHODS AND FINDINGS

We searched PubMed, Embase, bioRxiv, and medRxiv using a database of SARS-CoV-2 literature that is updated daily, on 25 March 2020, 20 April 2020, and 10 June 2020. Studies of people with SARS-CoV-2 diagnosed by reverse transcriptase PCR (RT-PCR) that documented follow-up and symptom status at the beginning and end of follow-up or modelling studies were included. One reviewer extracted data and a second verified the extraction, with disagreement resolved by discussion or a third reviewer. Risk of bias in empirical studies was assessed with an adapted checklist for case series, and the relevance and credibility of modelling studies were assessed using a published checklist. We included a total of 94 studies. The overall estimate of the proportion of people who become infected with SARS-CoV-2 and remain asymptomatic throughout infection was 20% (95% confidence interval [CI] 17-25) with a prediction interval of 3%-67% in 79 studies that addressed this review question. There was some evidence that biases in the selection of participants influence the estimate. In seven studies of defined populations screened for SARS-CoV-2 and then followed, 31% (95% CI 26%-37%, prediction interval 24%-38%) remained asymptomatic. The proportion of people that is presymptomatic could not be summarised, owing to heterogeneity. The secondary attack rate was lower in contacts of people with asymptomatic infection than those with symptomatic infection (relative risk 0.35, 95% CI 0.10-1.27). Modelling studies fit to data found a higher proportion of all SARS-CoV-2 infections resulting from transmission from presymptomatic individuals than from asymptomatic individuals. Limitations of the review include that most included studies were not designed to estimate the proportion of asymptomatic SARS-CoV-2 infections and were at risk of selection biases; we did not consider the possible impact of false negative RT-PCR results, which would underestimate the proportion of asymptomatic infections; and the database does not include all sources.

CONCLUSIONS

The findings of this living systematic review suggest that most people who become infected with SARS-CoV-2 will not remain asymptomatic throughout the course of the infection. The contribution of presymptomatic and asymptomatic infections to overall SARS-CoV-2 transmission means that combination prevention measures, with enhanced hand hygiene, masks, testing tracing, and isolation strategies and social distancing, will continue to be needed.

Occurrence and transmission potential of asymptomatic and presymptomatic SARS-CoV-2 infections: A living systematic review and meta-analysis

BACKGROUND

There is disagreement about the level of asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We conducted a living systematic review and meta-analysis to address three questions: (1) Amongst people who become infected with SARS-CoV-2, what proportion does not experience symptoms at all during their infection? (2) Amongst people with SARS-CoV-2 infection who are asymptomatic when diagnosed, what proportion will develop symptoms later? (3) What proportion of SARS-CoV-2 transmission is accounted for by people who are either asymptomatic throughout infection or presymptomatic?

METHODS AND FINDINGS

We searched PubMed, Embase, bioRxiv, and medRxiv using a database of SARS-CoV-2 literature that is updated daily, on 25 March 2020, 20 April 2020, and 10 June 2020. Studies of people with SARS-CoV-2 diagnosed by reverse transcriptase PCR (RT-PCR) that documented follow-up and symptom status at the beginning and end of follow-up or modelling studies were included. One reviewer extracted data and a second verified the extraction, with disagreement resolved by discussion or a third reviewer. Risk of bias in empirical studies was assessed with an adapted checklist for case series, and the relevance and credibility of modelling studies were assessed using a published checklist. We included a total of 94 studies. The overall estimate of the proportion of people who become infected with SARS-CoV-2 and remain asymptomatic throughout infection was 20% (95% confidence interval [CI] 17-25) with a prediction interval of 3%-67% in 79 studies that addressed this review question. There was some evidence that biases in the selection of participants influence the estimate. In seven studies of defined populations screened for SARS-CoV-2 and then followed, 31% (95% CI 26%-37%, prediction interval 24%-38%) remained asymptomatic. The proportion of people that is presymptomatic could not be summarised, owing to heterogeneity. The secondary attack rate was lower in contacts of people with asymptomatic infection than those with symptomatic infection (relative risk 0.35, 95% CI 0.10-1.27). Modelling studies fit to data found a higher proportion of all SARS-CoV-2 infections resulting from transmission from presymptomatic individuals than from asymptomatic individuals. Limitations of the review include that most included studies were not designed to estimate the proportion of asymptomatic SARS-CoV-2 infections and were at risk of selection biases; we did not consider the possible impact of false negative RT-PCR results, which would underestimate the proportion of asymptomatic infections; and the database does not include all sources.

CONCLUSIONS

The findings of this living systematic review suggest that most people who become infected with SARS-CoV-2 will not remain asymptomatic throughout the course of the infection. The contribution of presymptomatic and asymptomatic infections to overall SARS-CoV-2 transmission means that combination prevention measures, with enhanced hand hygiene, masks, testing tracing, and isolation strategies and social distancing, will continue to be needed.