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

Electrochemical biosensor for the evaluation of monoclonal antibodies targeting the N protein of SARS-CoV-2 virus

The emergence of COVID-19 caused by the coronavirus SARS-CoV-2 has prompted a global pandemic that requires continuous research and monitoring. This study presents a design of an electrochemical biosensing platform suitable for the evaluation of monoclonal antibodies targeting the SARS-CoV-2 nucleocapsid (N) protein. Screen-printed carbon electrodes (SPCE) modified with gold nanostructures (AuNS) were applied to design a versatile and sensitive sensing platform. Electrochemical techniques, including electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SWV), were used to investigate the interactions between immobilised recombinant N (rN) protein and several monoclonal antibodies (mAbs). The electrochemical characterisation of SPCE/AuNS/rN demonstrated a successful immobilisation of rN, enhancing the electron transfer kinetics. Affinity interactions between immobilised rN and four mAbs (mAb-4B3, mAb-4G6, mAb-12B2, and mAb-1G5) were explored. Although mAb-4B3 showed some non-linearity, the other monoclonal antibodies exhibited specific and well-defined interactions followed by the formation of an immune complex. The biosensing platform demonstrated high sensitivity in the linear range (LR) from 0.2 nM to 1 nM with limits of detection (LOD) ranging from 0.012 nM to 0.016 nM for mAb-4G6, mAb-12B2, and mAb-1G5 and limits of quantification (LOQ) values ranging from 0.035 nM to 0.139 nM, as determined by both EIS and SWV methods. These results highlight the system's potential for precise and selective detection of monoclonal antibodies specific to the rN. This electrochemical biosensing platform provides a promising route for the sensitive and accurate detection of monoclonal antibodies specific to the rN protein.

Identification of the needs of individuals affected by COVID-19

BACKGROUND

The optimal management of COVID-19 symptoms and their sequelae remains an important area of clinical research. Policy makers have little scientific data regarding the effects on the daily life of affected individuals and the identification of their needs. Such data are needed to inform effective care policy.

METHODS

We studied 639 people with COVID-19 resident in France via an online questionnaire. They reported their symptoms, effects on daily life, and resulting needs, with particular focus on olfaction.

RESULTS

The results indicate that a majority of participants viewed their symptoms as disabling, with symptoms affecting their physical and mental health, social and professional lives. 60% of the individuals reported having unmet medical, psychological and socio-professional support needs. Finally, affected individuals were concerned about the risk and invasiveness of possible treatments as shown by a preference for non-invasive intervention over surgery to cure anosmia.

CONCLUSIONS

It is important that policy makers take these needs into consideration in order to assist affected individuals to regain a normal quality of life.

SARS-CoV-2 Viral Load in the Nasopharynx at Time of First Infection Among Unvaccinated Individuals: A Secondary Cross-Protocol Analysis of 4 Randomized Trials

Importance

SARS-CoV-2 viral load (VL) in the nasopharynx is difficult to quantify and standardize across settings, but it may inform transmission potential and disease severity.

Objective

To characterize VL at COVID-19 diagnosis among previously uninfected and unvaccinated individuals by evaluating the association of demographic and clinical characteristics, viral variant, and trial with VL, as well as the ability of VL to predict severe disease.

Design, Setting, and Participants

This secondary cross-protocol analysis used individual-level data from placebo recipients from 4 harmonized, phase 3 COVID-19 vaccine efficacy trials sponsored by Moderna, AstraZeneca, Janssen, and Novavax. Participants were SARS-CoV-2 negative at baseline and acquired COVID-19 during the blinded phase of the trials. The setting included the US, Brazil, South Africa, Colombia, Argentina, Peru, Chile, and Mexico; start dates were July 27, 2020, to December 27, 2020; data cutoff dates were March 26, 2021, to July 30, 2021. Statistical analysis was performed from November 2022 to June 2023.

Main Outcomes and Measures

Linear regression was used to assess the association of demographic and clinical characteristics, viral variant, and trial with polymerase chain reaction-measured log10 VL in nasal and/or nasopharyngeal swabs taken at the time of COVID-19 diagnosis.

Results

Among 1667 participants studied (886 [53.1%] male; 995 [59.7%] enrolled in the US; mean [SD] age, 46.7 [14.7] years; 204 [12.2%] aged 65 years or older; 196 [11.8%] American Indian or Alaska Native, 150 [9%] Black or African American, 1112 [66.7%] White; 762 [45.7%] Hispanic or Latino), median (IQR) log10 VL at diagnosis was 6.18 (4.66-7.12) log10 copies/mL. Participant characteristics and viral variant explained only 5.9% of the variability in VL. The independent factor with the highest observed differences was trial: Janssen participants had 0.54 log10 copies/mL lower mean VL vs Moderna participants (95% CI, 0.20 to 0.87 log10 copies/mL lower). In the Janssen study, which captured the largest number of COVID-19 events and variants and used the most intensive post-COVID surveillance, neither VL at diagnosis nor averaged over days 1 to 28 post diagnosis was associated with COVID-19 severity.

Conclusions and Relevance

In this study of placebo recipients from 4 randomized phase 3 trials, high variability was observed in SARS-CoV-2 VL at the time of COVID-19 diagnosis, and only a fraction was explained by individual participant characteristics or viral variant. These results suggest challenges for future studies of interventions seeking to influence VL and elevates the importance of standardized methods for specimen collection and viral load quantitation.

Workplace interventions to reduce the risk of SARS-CoV-2 infection outside of healthcare settings

BACKGROUND

Although many people infected with SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) experience no or mild symptoms, some individuals can develop severe illness and may die, particularly older people and those with underlying medical problems. Providing evidence-based interventions to prevent SARS-CoV-2 infection has become more urgent with the potential psychological toll imposed by the coronavirus disease 2019 (COVID-19) pandemic. Controlling exposures to occupational hazards is the fundamental method of protecting workers. When it comes to the transmission of viruses, workplaces should first consider control measures that can potentially have the most significant impact. According to the hierarchy of controls, one should first consider elimination (and substitution), then engineering controls, administrative controls, and lastly, personal protective equipment. This is the first update of a Cochrane review published 6 May 2022, with one new study added.

OBJECTIVES

To assess the benefits and harms of interventions in non-healthcare-related workplaces aimed at reducing the risk of SARS-CoV-2 infection compared to other interventions or no intervention.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, Web of Science Core Collections, Cochrane COVID-19 Study Register, World Health Organization (WHO) COVID-19 Global literature on coronavirus disease, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform, and medRxiv to 13 April 2023.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and non-randomised studies of interventions. We included adult workers, both those who come into close contact with clients or customers (e.g. public-facing employees, such as cashiers or taxi drivers), and those who do not, but who could be infected by coworkers. We excluded studies involving healthcare workers. We included any intervention to prevent or reduce workers' exposure to SARS-CoV-2 in the workplace, defining categories of intervention according to the hierarchy of hazard controls (i.e. elimination; engineering controls; administrative controls; personal protective equipment).

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were incidence rate of SARS-CoV-2 infection (or other respiratory viruses), SARS-CoV-2-related mortality, adverse events, and absenteeism from work. Our secondary outcomes were all-cause mortality, quality of life, hospitalisation, and uptake, acceptability, or adherence to strategies. We used the Cochrane RoB 2 tool to assess risk of bias, and GRADE methods to evaluate the certainty of evidence for each outcome.

MAIN RESULTS

We identified 2 studies including a total of 16,014 participants. Elimination-of-exposure interventions We included one study examining an intervention that focused on elimination of hazards, which was an open-label, cluster-randomised, non-inferiority trial, conducted in England in 2021. The study compared standard 10-day self-isolation after contact with an infected person to a new strategy of daily rapid antigen testing and staying at work if the test is negative (test-based attendance). The trialists hypothesised that this would lead to a similar rate of infections, but lower COVID-related absence. Staff (N = 11,798) working at 76 schools were assigned to standard isolation, and staff (N = 12,229) working at 86 schools were assigned to the test-based attendance strategy. The results between test-based attendance and standard 10-day self-isolation were inconclusive for the rate of symptomatic polymerase chain reaction (PCR)-positive SARS-CoV-2 infection (rate ratio (RR) 1.28, 95% confidence interval (CI) 0.74 to 2.21; 1 study; very low-certainty evidence). The results between test-based attendance and standard 10-day self-isolation were inconclusive for the rate of any PCR-positive SARS-CoV-2 infection (RR 1.35, 95% CI 0.82 to 2.21; 1 study; very low-certainty evidence). COVID-related absenteeism rates were 3704 absence days in 566,502 days-at-risk (6.5 per 1000 working days) in the control group and 2932 per 539,805 days-at-risk (5.4 per 1000 working days) in the intervention group (RR 0.83, 95% CI 0.55 to 1.25). We downgraded the certainty of the evidence to low due to imprecision. Uptake of the intervention was 71% in the intervention group, but not reported for the control intervention. The trial did not measure our other outcomes of SARS-CoV-2-related mortality, adverse events, all-cause mortality, quality of life, or hospitalisation. We found seven ongoing studies using elimination-of-hazard strategies, six RCTs and one non-randomised trial. Administrative control interventions We found one ongoing RCT that aims to evaluate the efficacy of the Bacillus Calmette-Guérin (BCG) vaccine in preventing COVID-19 infection and reducing disease severity. Combinations of eligible interventions We included one non-randomised study examining a combination of elimination of hazards, administrative controls, and personal protective equipment. The study was conducted in two large retail companies in Italy in 2020. The study compared a safety operating protocol, measurement of body temperature and oxygen saturation upon entry, and a SARS-CoV-2 test strategy with a minimum activity protocol. Both groups received protective equipment. All employees working at the companies during the study period were included: 1987 in the intervention company and 1798 in the control company. The study did not report an outcome of interest for this systematic review. Other intervention categories We did not find any studies in this category.

AUTHORS' CONCLUSIONS

We are uncertain whether a test-based attendance policy affects rates of PCR-positive SARS-CoV-2 infection (any infection; symptomatic infection) compared to standard 10-day self-isolation amongst school and college staff. A test-based attendance policy may result in little to no difference in absenteeism rates compared to standard 10-day self-isolation. The non-randomised study included in our updated search did not report any outcome of interest for this Cochrane review. As a large part of the population is exposed in the case of a pandemic, an apparently small relative effect that would not be worthwhile from the individual perspective may still affect many people, and thus become an important absolute effect from the enterprise or societal perspective. The included RCT did not report on any of our other primary outcomes (i.e. SARS-CoV-2-related mortality and adverse events). We identified no completed studies on any other interventions specified in this review; however, eight eligible studies are ongoing. More controlled studies are needed on testing and isolation strategies, and working from home, as these have important implications for work organisations.

Vaccination strategies impact the probability of outbreak extinction: A case study of COVID-19 transmission

Mass vaccination has proven to be an effective control measure for mitigating the transmission of infectious diseases. Throughout history, various vaccination strategies have been employed to control infections and terminate outbreaks. In this study, we utilized the transmission of COVID-19 as a case study and constructed a stochastic age-structured compartmental model to investigate the effectiveness of different vaccination strategies. Our analysis focused on estimating the outbreak extinction probability under different vaccination scenarios in both homogeneous and heterogeneous populations. Notably, we found that population heterogeneity can enhance the likelihood of outbreak extinction at varying levels of vaccine coverage. Prioritizing vaccinations for individuals with higher infection risk was found to maximize outbreak extinction probability and reduce overall infections, while allocating vaccines to those with higher mortality risk has been proven more effective in reducing deaths. Moreover, our study highlighted the significance of booster doses as the vaccine effectiveness wanes over time, showing that they can significantly enhance the extinction probability and mitigate disease transmission.

Interrogating the lack of diversity of thought in the pandemic response that led to mistakes - holistic evidence-based approach to deal with future pandemics

The COVID-19 pandemic, triggered by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), rapidly became a worldwide emergency. How it was managed garnered both commendation and vehement censure. This crisis profoundly affected healthcare, the economy, education, and public confidence in scientific endeavors. Our primary aim was to scrutinize the shortcomings in the pandemic management and to articulate a more effective strategy for handling prospective pandemics. We delved into the errors encountered in the COVID-19 response and posited a holistic, evidence-grounded approach for future pandemic mitigation.

Operational strategies to deal with the COVID-19 emergency: recommendations from the Italian national society SIAGASCOT following the introduction of vaccines against the SARS-CoV-2 infection

BACKGROUND

This article aims to present the operational recommendations adopted by the Italian national society for orthopaedic surgery, arthroscopy, and sports medicine (SIAGASCOT) in managing patients eligible to undergo elective orthopaedic surgery during the COVID-19 pandemic after the beginning of a national vaccination campaign.

MATERIALS AND METHODS

An extensive literature search, analysing medical databases and scientific societies protocols, was performed to support this document. A four-step approach was used: 1-definition of priorities; 2-definition of significant clusters of interventions; 3-extraction of recommendations from international literature; and 4-adaptation of the recommendations to the specific features of the Italian healthcare system.

RESULTS

Three operational priorities were defined ("continuity of care and containment of the virus spread", "examination of waiting lists", and "definition of the role of vaccines"), six significant clusters of intervention were identified, and recommendations regarding the risk management for healthcare staff and hospital facility as well as the preoperative, in-hospital, and postoperative management were produced. Patient selection, preoperative screening, and pre-hospitalization procedures, which are regarded as pivotal roles in the safe management of patients eligible to undergo elective orthopaedic surgery, were analysed extensively.

CONCLUSIONS

This document presents national-wide recommendations for managing patients eligible to undergo elective orthopaedic surgery with the beginning of the vaccination campaign. This paper could be the basis for similar documents adapted to the local healthcare systems in other countries.

LEVEL OF EVIDENCE

Level IV.

Transmission dynamics, responses, and clinical features for the first 1100 COVID-19 cases in South Batinah, Oman: Major lessons from a provincial perspective

Objectives

This study was aimed at exploring and analyzing the epidemiological profile, surveillance, and response to COVID-19, including transmission dynamics and cluster formation.

Methodology

This was a retrospective analysis of surveillance data, including contact tracing, risk factors, and clinical information. Binary logistic regressions were used to assess the likelihood of admission, cluster formation, and of each individual being an index patient. Clusters were demonstrated through geographic data systems, network analysis, and visualization software.

Results

A total of 1100 COVID-19 cases were diagnosed from 20 March to 7 June 2020, of which 144 (13.1%) were asymptomatic. The median time from symptom onset to admission was 7 days (IQR, 4.5-10), and the median symptom duration was 5 days (IQR, 3-9). Eighty-nine clusters containing 736 patients were identified. The surveillance and control actions were divided into three phases. Clusters began to form in phase 2 and became more pronounced in phase 3. Patients ≥50 years of age and patients presenting with fever had relatively higher odds of admission: OR = 12.85 (95% CI 5.13-32.19) and 2.53 (95% CI 1.24-5.17), respectively. Cluster formation was observed among females, asymptomatic patients, and people living in Awabi: OR = 2.3 (95% CI 1.7-3.1), 6.39 (95% CI 2.33-17.2), and 3.54 (95% CI 2.06-6.07), respectively. Patients working in the police and defense sectors had higher odds of being an index patient: OR = 7.88 (95% CI 3.35-18.52).

Conclusion

Case-based interventions should be supported by population-wide measures, particularly movement restrictions. Establishing prevention teams or district units, or primary care will be crucial for the control of future pandemics. Prevention should always be prioritized for vulnerable populations.

A 12-month follow-up of the immune response to SARS-CoV-2 primary vaccination: evidence from a real-world study

A real-world population-based longitudinal study, aimed at determining the magnitude and duration of immunity induced by different types of vaccines against COVID-19, started in 2021 by enrolling a cohort of 2,497 individuals at time of their first vaccination. The study cohort included both healthy adults aged ≤65 years and elderly subjects aged >65 years with two or more co-morbidities. Here, patterns of anti-SARS-CoV-2 humoral and cell-mediated specific immune response, assessed on 1,182 remaining subjects, at 6 (T6) and 12 months (T12) after the first vaccine dose, are described. At T12 median anti-Spike IgG antibody levels were increased compared to T6. The determinants of increased anti-Spike IgG were the receipt of a third vaccine dose between T6 and T12 and being positive for anti-Nucleocapside IgG at T12, a marker of recent infection, while age had no significant effect. The capacity of T12 sera to neutralize in vitro the ancestral B strain and the Omicron BA.5 variant was assessed in a subgroup of vaccinated subjects. A correlation between anti-S IgG levels and sera neutralizing capacity was identified and higher neutralizing capacity was evident in healthy adults compared to frail elderly subjects and in those who were positive for anti-Nucleocapside IgG at T12. Remarkably, one third of T12 sera from anti-Nucleocapside IgG negative older individuals were unable to neutralize the BA.5 variant strain. Finally, the evaluation of T-cell mediated immunity showed that most analysed subjects, independently from age and comorbidity, displayed Spike-specific responses with a high degree of polyfunctionality, especially in the CD8 compartment. In conclusion, vaccinated subjects had high levels of circulating antibodies against SARS-CoV-2 Spike protein 12 months after the primary vaccination, which increased as compared to T6. The enhancing effect could be attributable to the administration of a third vaccine dose but also to the occurrence of breakthrough infection. Older individuals, especially those who were anti-Nucleocapside IgG negative, displayed an impaired capacity to neutralize the BA.5 variant strain. Spike specific T-cell responses, able to sustain immunity and maintain the ability to fight the infection, were present in most of older and younger subjects assayed at T12.

Understanding adherence to self-isolation in the first phase of the COVID-19 pandemic in England: a cross-sectional mixed-methods study

BACKGROUND

During the early "containment" phase of the COVID-19 response in England (January-March 2020), contact tracing was managed by Public Health England (PHE). Adherence to self-isolation during this phase and how people were making those decisions has not previously been determined. The aim of this study was to gain a better understanding of decisions around adherence to self-isolation during the first phase of the COVID-19 response in England.

METHODS

A mixed-methods cross sectional study was conducted, including an online survey and qualitative interviews. The overall pattern of adherence was described as never leaving home, leaving home for lower-contact reasons and leaving home for higher-contact reasons. Fisher's exact test was used to test associations between adherence and potentially predictive binary factors. Factors showing evidence of association overall were then considered in relation to the three aspects of adherence individually. Qualitative data were analysed using inductive thematic analysis.

RESULTS

Of 250 respondents who were advised to self-isolate, 63% reported not leaving home at all during their isolation period, 20% reported leaving only for lower-contact activities (dog walking or exercise) and 16% reported leaving for higher-contact, and therefore higher-risk, reasons. Factors associated with adherence to never going out included: the belief that following isolation advice would save lives, experiencing COVID-19 symptoms, being advised to stay in their room, having help from outside and having regular contact by text message from PHE. Factors associated with non-adherence included being angry about the advice to isolate, being unable to get groceries delivered and concerns about losing touch with friends and family. Interviews highlighted that a sense of duty motivated people to adhere to isolation guidance and where people did leave their homes, these decisions were based on rational calculations of the risk of transmission - people would only leave their homes when they thought they were unlikely to come into contact with others.

CONCLUSIONS

Understanding adherence to isolation and associated reasoning during the early stages of the pandemic is essential to pandemic preparedness for future emerging infectious disease outbreaks. Individuals make complex decisions around adherence by calibrating transmission risks, therefore treating adherence as binary should be avoided.

Evaluating the impact of testing strategies for the detection of nosocomial COVID-19 in English hospitals through data-driven modeling

Introduction

During the first wave of the COVID-19 pandemic 293,204 inpatients in England tested positive for SARS-CoV-2. It is estimated that 1% of these cases were hospital-associated using European centre for disease prevention and control (ECDC) and Public Health England (PHE) definitions. Guidelines for preventing the spread of SARS-CoV-2 in hospitals have developed over time but the effectiveness and efficiency of testing strategies for preventing nosocomial transmission has not been explored.

Methods

Using an individual-based model, parameterised using multiple datasets, we simulated the transmission of SARS-CoV-2 to patients and healthcare workers between March and August 2020 and evaluated the efficacy of different testing strategies. These strategies were: 0) Testing only symptomatic patients on admission; 1) Testing all patients on admission; 2) Testing all patients on admission and again between days 5 and 7, and 3) Testing all patients on admission, and again at days 3, and 5-7. In addition to admissions testing, patients that develop a symptomatic infection while in hospital were tested under all strategies. We evaluated the impact of testing strategy, test characteristics and hospital-related factors on the number of nosocomial patient infections.

Results

Modelling suggests that 84.6% (95% CI: 84.3, 84.7) of community-acquired and 40.8% (40.3, 41.3) of hospital-associated SARS-CoV-2 infections are detectable before a patient is discharged from hospital. Testing all patients on admission and retesting after 3 or 5 days increases the proportion of nosocomial cases detected by 9.2%. Adding discharge testing increases detection by a further 1.5% (relative increase). Increasing occupancy rates, number of beds per bay, or the proportion of admissions wrongly suspected of having COVID-19 on admission and therefore incorrectly cohorted with COVID-19 patients, increases the rate of nosocomial transmission. Over 30,000 patients in England could have been discharged while incubating a non-detected SARS-CoV-2 infection during the first wave of the COVID-19 pandemic, of which 3.3% could have been identified by discharge screening. There was no significant difference in the rates of nosocomial transmission between testing strategies or when the turnaround time of the test was increased.

Discussion

This study provides insight into the efficacy of testing strategies in a period unbiased by vaccines and variants. The findings are relevant as testing programs for SARS-CoV-2 are scaled back, and possibly if a new vaccine escaping variant emerges.

Seroprevalence of Anti-SARS-CoV-2 IgG and IgM Antibodies among Government Employees in Iran

The COVID-19 disease emerged in Wuhan, China, in December 2019 and quickly became a global health threat. Around 6,947,192 people have been killed around the world so far, including 146,292 in Iran. In addition to the definitive diagnosis of the disease by RT-PCR, immunological and serological tests can check the anti-SARS-CoV-2 N protein antibody titer in people at different stages of infection with acceptable sensitivity and specificity. The serological examination is an effective and efficient method for determining the prevalence of the disease, especially when asymptomatic cases are present or the diagnosis of symptomatic cases is incomplete. The study examined the seroprevalence of COVID-19 at the Razi Vaccine and Serum Research Institute (RVSRI) and the Agricultural Research, Education, and Extension Organization (AREEO). A total of 493 blood samples were collected from volunteers in June 2020 in AREEO, and 380 samples were collected in June and July 2020 in RVSRI. The total number of volunteers from both organizations was 873. Standard ELISA kits were used to measure IgG and IgM antibodies against SARS-CoV-2. A statistical analysis of the obtained data was conducted using SPSS (version 22.0). Among the total 873 volunteers examined in RVSRI and AREEO, 10.5% had elevated serum titers either for IgM or IgG, 3.55% of whom were women and 6.95% were men. Generally, 8.8% of people tested positive for IgM, which showed a recent infection with COVID-19 in people at that time and partially indicated the start of a new wave of COVID-19. In RVSRI, 3.42% of people with positive IgM titers (positive or negative IgG titers) were women and 5.53% were men. In AREEO, 3.02% were women and 5.72% were men. The seroprevalence rate of COVID-19 in RVSRI was 11.6%, 4.2% of which were women and 7.35% were men, with no significant difference between women and men. The COVID-19 seroprevalence in AREEO was 9.7%, 3.22% of which were women and 6.5% were men, with no significant difference between women and men.

Dynamics analysis of strangles with asymptomatic infected horses and long-term subclinical carriers

Strangles is one of the most prevalent horse diseases globally. The infected horses may be asymptomatic and can still carry the infectious pathogen after it recovers, which are named asymptomatic infected horses and long-term subclinical carriers, respectively. Based on these horses, this paper establishes a dynamical model to screen, measure, and model the spread of strangles. The basic reproduction number $ \mathcal{R}_0 $ is computed through a next generation matrix method. By constructing Lyapunov functions, we concluded that the disease-free equilibrium is globally asymptotically stable if $ \mathcal{R}_0 < 1 $, and the endemic equilibrium exits uniquely and is globally asymptotically stable if $ \mathcal{R}_0 > 1 $. For example, while studying a strangles outbreak of a horse farm in England in 2012, we computed an $ \mathcal{R}_0 = 0.8416 $ of this outbreak by data fitting. We further conducted a parameter sensitivity analysis of $ \mathcal{R}_0 $ and the final size by numerical simulations. The results show that the asymptomatic horses mainly influence the final size of this outbreak and that long-term carriers are connected to an increased recurrence of strangles. Moreover, in terms of the three control measures implemented to control strangles(i.e., vaccination, implementing screening regularly and isolating symptomatic horses), the result shows that screening is the most effective measurement, followed by vaccination and isolation, which can provide effective guidance for horse management.

A Scalar Approach to Vaccination Ethics

Should people get vaccinated for the sake of others? What could ground-and limit-the normative claim that people ought to do so? In this paper, we propose a reasons-based consequentialist account of vaccination for the benefit of others. We outline eight harm-based and probabilistic factors that, we argue, give people moral reasons to get vaccinated. Instead of understanding other-directed vaccination in terms of binary moral duties (i.e., where people either have or do not have a moral duty to get vaccinated), we develop a scalar approach according to which people can have stronger or weaker moral reasons to get vaccinated in view of the moral good of vaccination. One advantage of our approach is that it can capture why a person might have strong moral reasons to get vaccinated with Vaccine A, but only weak moral reasons to get vaccinated with Vaccine B. We discuss theoretical strengths of our approach and provide a case study of vaccination against COVID-19 to demonstrate its practical significance.

Korea Seroprevalence Study of Monitoring of SARS-COV-2 Antibody Retention and Transmission (K-SEROSMART): findings from national representative sample

OBJECTIVES

We estimated the population prevalence of antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), including unreported infections, through a Korea Seroprevalence Study of Monitoring of SARS-CoV-2 Antibody Retention and Transmission (K-SEROSMART) in 258 communities throughout Korea.

METHODS

In August 2022, a survey was conducted among 10,000 household members aged 5 years and older, in households selected through two stage probability random sampling. During face-to-face household interviews, participants self-reported their health status, COVID-19 diagnosis and vaccination history, and general characteristics. Subsequently, participants visited a community health center or medical clinic for blood sampling. Blood samples were analyzed for the presence of antibodies to spike proteins (anti-S) and antibodies to nucleocapsid proteins (anti-N) SARS-CoV-2 proteins using an electrochemiluminescence immunoassay. To estimate the population prevalence, the PROC SURVEYMEANS statistical procedure was employed, with weighting to reflect demographic data from July 2022.

RESULTS

In total, 9,945 individuals from 5,041 households were surveyed across 258 communities, representing all basic local governments in Korea. The overall population-adjusted prevalence rates of anti-S and anti-N were 97.6% and 57.1%, respectively. Since the Korea Disease Control and Prevention Agency has reported a cumulative incidence of confirmed cases of 37.8% through July 31, 2022, the proportion of unreported infections among all COVID-19 infection was suggested to be 33.9%.

CONCLUSIONS

The K-SEROSMART represents the first nationwide, community-based seroepidemiologic survey of COVID-19, confirming that most individuals possess antibodies to SARS-CoV-2 and that a significant number of unreported cases existed. Furthermore, this study lays the foundation for a surveillance system to continuously monitor transmission at the community level and the response to COVID-19.

Revisiting the rationale of mandatory masking

In this perspective, we review the evidence for the efficacy of face masks to reduce the transmission of respiratory viruses, specifically severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and consider the value of mandating universal mask wearing against the widespread negative impacts that have been associated with such measures. Before the SARS-CoV-2 pandemic, it was considered that there was little to no benefit in healthy people wearing masks as prophylaxis against becoming infected or as unwitting vectors of viral transmission. This accepted policy was hastily reversed early on in the pandemic, when districts and countries throughout the world imposed stringent masking mandates. Now, more than three years since the start of the pandemic, the amassed studies that have investigated the use of masks to reduce transmission of SARS-CoV-2 (or other pathogens) have led to conclusions that are largely inconsistent and contradictory. There is no statistically significant or unambiguous scientific evidence to justify mandatory masking for general, healthy populations with the intention of lessening the viral spread. Even if mask wearing could potentially reduce the transmission of SARS-CoV-2 in individual cases, this needs to be balanced against the physical, psychological and social harms associated with forced mask wearing, not to mention the negative impact of innumerable disposed masks entering our fragile environment. Given the lack of unequivocal scientific proof that masks have any effect on reducing transmission, together with the evident harms to people and the environment through the use of masks, it is our opinion that the mandatory use of face masks in the general population is unjustifiable and must be abandoned in future pandemic countermeasures policies.

How Reactivation of SARS-CoV-2 in Astronauts with Dysregulated Immune Systems Can Negatively Affect the Odds of Success in Future Space Missions

We have previously reported that during future space missions the risk of severe COVID-19 infection will be a cardinal issue that needs careful attention. Our studies show that even with the most reliable pre-mission screening and quarantine strategies, astronauts with a latent (hidden, inactive, or dormant) SARS-CoV-2 infection might be sent to space. Given this consideration, an asymptomatic individual with dormant SARS-CoV-2 infection may successfully pass all the pre-launch medical tests. Then during a space mission such as a journey to Mars or beyond, when the immune system of these astronauts starts to weaken, the dormant infection may progress to a severe infection that possibly affects the chance of the mission's success. The effects of microgravity and the elevated space radiation are two key factors that should be evaluated. Furthermore, the limited size of the spacecraft, the proximity of crew members during flight operations, spacecraft atmospheric composition, limited exercise capability, effects of viral response to space radiation, and uncertainty in the likelihood of the virus to mutate and evolve during a space mission merit additional study.

Effects of Smoking on COVID-19 Management and Mortality: An Umbrella Review

Introduction

Smoking status appears to lead to a poor prognosis in COVID-19 patients. However, findings from the studies conducted on this topic have not been consistent, and further exploration is required.

Methods

The objective of this umbrella review was to examine the effects of smoking on COVID-19 management and mortality. Online databases that included PubMed, Embase, Scopus, and Web of Science were searched using relevant keywords up to July 27, 2022. Articles were restricted to the English language, and the PRISMA protocol was followed.

Results

A total of 27 systematic reviews, published from 2020 to 2022, were included. Individual studies included in the systematic reviews ranged from 8 to 186, with various population sizes. The consensus from the majority of systematic reviews was that COVID-19 smoker patients experience greater disease severity, disease progression, hospitalization rate, hospital admission duration, mechanical ventilation, ICU admission, and mortality rate.

Conclusions

COVID-19 patients with a history of smoking (current and former) are vulnerable to adverse hospital outcomes and worse COVID-19 progression. Effective preventive and supportive approaches are required to decrease the risk of COVID-19 morbidity and mortality in patients with a history of smoking.

Environmental factors and their impact on the COVID-19 pandemic

The coronavirus disease 2019 (COVID-19) pandemic has resulted in numerous cases of illness and death worldwide. Research has shown that there are associations between transmission, as well as the severity of SARS-CoV‑2 (severe acute respiratory syndrome coronavirus 2) infections, and various environmental factors. For example, air pollution with particulate matter is thought to play a crucial role, and both climatic and geographical aspects must be considered. Furthermore, environmental conditions such as industry and urban lifestyle have a significant impact on air quality and thus on health aspects of the population. In this regard, other factors such as chemicals, microplastics, and diet also critically impact health, including respiratory and cardiovascular diseases. Overall, the COVID-19 pandemic has highlighted how closely health and the environment are linked. This review discusses the impact of environmental factors on the COVID-19 pandemic.

Transportation as a Disease Vector in COVID-19: Border Mobility and Disease Spread

More than a year after COVID-19 was declared a pandemic by the World Health Organization, the U.S.A. and Mexico rank first and fourth, respectively, with regard to the number of deaths. From March 2020, nonessential travelers were not allowed to cross the border into the U.S.A. from Mexico via international land ports of entry, which resulted in a more than 50% decrease in the number of people crossing the border. However, border communities still face a higher number of cases and faster community spread compared with those without international land ports of entry. This paper established an econometric model to understand the effects of cross-border mobility and other socioeconomic parameters on the speed of spread. The model was developed at the U.S. county level using data from all 3,141 counties in the U.S.A. Additionally, a follow-up U.S. county comparative analysis was developed to examine the significance of having a border crossing between the U.S.A. and Mexico for U.S. counties. The findings of the analysis revealed that the variables having a significant effect are as follows: population density; number of people per household; population in the 15-65 age group; median household income; mask use; number of visits to transit stations; number of visits to workplace; overall mobility; and having a border crossing to Mexico within county limits. The comparative analysis found that U.S. counties with border crossings have an average of 123 cases per 1,000 population whereas their counterparts without border crossings only have 90 cases per 1,000 population.

Non-HIV-related comorbidities and uncontrolled HIV replication are independent factors increasing the odds of hospitalization due to COVID-19 among HIV-positive patients in Poland

PURPOSE

Immunocompromised patients are postulated to be at elevated risk of unfavorable outcomes of COVID-19. The exact effect of HIV infection on the course of COVID-19 remains to be elucidated. The aim of the study was to describe the epidemiological and clinical aspects of SARS-CoV-2 infection in HIV-infected individuals.

METHODS

The HIV-positive patients who were diagnosed with SARS-CoV-2 infection were identified through thirteen specialist HIV clinics routinely following them due to HIV treatment. The data were collected between November 2020 and May 2021 through an on-line electronical case report form (SurveyMonkey®). The collected information included demographics, lifestyle, comorbidities, HIV care history, COVID-19 clinical course and treatment. Logistic regression models were used to identify factors associated with the odds of death or hospitalization due to COVID-19.

RESULTS

One hundred and seventy-three patients with HIV-SARS-CoV-2 coinfection were included in the analysis. One hundred and sixty-one (93.1%) subjects had a symptomatic course of the disease. Thirty-nine (23.1%) of them were hospitalized, 23 (13.3%) necessitated oxygen therapy. Three (1.8%) patients required admission to the intensive care unit and 6 (3.5%) patients died. The presence of comorbidities and an HIV viral load of more than 50 copies/mL were linked to the increased odds of hospitalization (OR 3.24 [95% CI 1.27-8.28]) and OR 5.12 [95% CI 1.35-19.6], respectively).

CONCLUSIONS

As depicted by our analyses, HIV-positive patients with comorbidities and/or uncontrolled HIV replication who are diagnosed with SARS-CoV-2 infection should be considered of high risk of poor COVID-19 outcome and followed up carefully.

How Asymptomatic Transmission Influences Mitigation and Suppression Strategies during a Pandemic

Asymptomatic transmission complicates any public health strategies to combat a pandemic, which proved especially accurate in the case of COVID-19. Although asymptomatic cases are not unique to COVID-19, the high asymptomatic case rate raised many problems for developing effective public health interventions. The current modeling effort explored how asymptomatic transmission might impact pandemic responses in four key areas: isolation procedures, changes in reproduction rate, the potential for reduced transmission from asymptomatic cases, and social adherence to public health measures. A high rate of asymptomatic cases effectively requires large-scale public health suppression and mitigation procedures given that quarantine procedures alone could not prevent an outbreak for a virus such as SARS-CoV-2. This problem only becomes worse without lowering the effective reproduction rate, and even assuming the potential for reduced transmission, any virus with a high degree of asymptomatic transmission will likely produce a pandemic. Finally, there is a concern that asymptomatic individuals will also refuse to adhere to public health guidance. Analyses indicate that, given certain assumptions, even half of the population adhering to public health guidance could reduce the peak and flatten the curve by over 90%. Taken together, these analyses highlight the importance of taking asymptomatic cases into account when modeling viral spread and developing public health intervention strategies.

Do pathogens always evolve to be less virulent? The virulence–transmission trade-off in light of the COVID-19 pandemic

The direction the evolution of virulence takes in connection with any pathogen is a long-standing question. Formerly, it was theorized that pathogens should always evolve to be less virulent. As observations were not in line with this theoretical outcome, new theories emerged, chief among them the transmission–virulence trade-off hypotheses, which predicts an intermediate level of virulence as the endpoint of evolution. At the moment, we are very much interested in the future evolution of COVID-19’s virulence. Here, we show that the disease does not fulfill all the assumptions of the hypothesis. In the case of COVID-19, a higher viral load does not mean a higher risk of death; immunity is not long-lasting; other hosts can act as reservoirs for the virus; and death as a consequence of viral infection does not shorten the infectious period. Consequently, we cannot predict the short- or long-term evolution of the virulence of COVID-19.

Asymptomatic surveillance testing for COVID-19 in health care professional students: lessons learned from a low prevalence setting

The novel coronavirus disease of 2019 (COVID-19) pandemic has severely impacted the training of health care professional students because of concerns of potential asymptomatic transmission to colleagues and vulnerable patients. From May 27th, 2020, to June 23rd 2021; at a time when B.1.1.7 (alpha) and B.1.617.2 (delta) were the dominant circulating variants, PCR testing was conducted on 1,237 nasopharyngeal swabs collected from 454 asymptomatic health care professional students as they returned to their studies from across Canada to Kingston, ON, a low prevalence area during that period for COVID-19. Despite 46.7% of COVID-19 infections occurring in the 18-29 age group in Kingston, severe-acute-respiratory coronavirus-2 was not detected in any of the samples suggesting that negligible asymptomatic infection occurred in this group and that PCR testing in this setting may not be warranted as a screening tool.

Delayed seropositivity is associated with lower levels of SARS-CoV-2 antibody levels in patients with mild to moderate COVID-19

BACKGROUND

Patients with COVID-19 can develop a range of immune responses, including variations in the onset and magnitude of antibody formation. The aim of this study was to investigate whether SARS-CoV-2 antibody levels vary in patients with mild to moderate COVID-19 in relation to the onset (days) of their post-symptom seropositivity and to explore host factors that may affect antibody production METHODS: This was a prospective, multiple measurements study involving 92 PCR-confirmed patients with mild to moderate COVID-19. Antibody testing for anti-nucleocapsid (anti-NP) and spike proteins (anti-S) was performed using ELISA tests. Serum samples were collected over a period of 55 days from symptom onset of COVID-19 infection, and repeated as necessary until they turned positive.

RESULTS

No significant differences were found between the positivity rates of anti-S or anti-NP regarding any clinical symptom (p > 0.05). The majority of patients who tested positive for anti-NP and anti-S showed early seropositivity (within 15 days of symptom onset) (75.9% for anti-NP and 82.6% for anti-S). Younger patients, those without chronic diseases, and non-healthcare workers had the highest percentage of seroconversion after day 35 post-symptom onset (p = 0.002, 0.028, and 0.036, respectively), while older patients and those with chronic diseases had earlier seropositivity and higher anti-NP levels (p = 0.003 and 0.06, respectively). Significantly higher anti-S ratios were found among older (p = 0.004), male (p = 0.015), and anemic patients (p = 0.02). A significant correlation was found between both antibodies (p = 0.001). At the end of the study, the cumulative seroconversion rate for both antibodies was almost 99%.

CONCLUSIONS

Some COVID-19 patients may exhibit delayed and weak immune responses, while elderly, anemic patients and those with chronic diseases may show earlier and higher antibody responses.

Effectiveness of feedback control and the trade-off between death by COVID-19 and costs of countermeasures

We provided a framework of a mathematical epidemic modeling and a countermeasure against the novel coronavirus disease (COVID-19) under no vaccines and specific medicines. The fact that even asymptomatic cases are infectious plays an important role for disease transmission and control. Some patients recover without developing the disease; therefore, the actual number of infected persons is expected to be greater than the number of confirmed cases of infection. Our study distinguished between cases of confirmed infection and infected persons in public places to investigate the effect of isolation. An epidemic model was established by utilizing a modified extended Susceptible-Exposed-Infectious-Recovered model incorporating three types of infectious and isolated compartments, abbreviated as SEIIIHHHR. Assuming that the intensity of behavioral restrictions can be controlled and be divided into multiple levels, we proposed the feedback controller approach to implement behavioral restrictions based on the active number of hospitalized persons. Numerical simulations were conducted using different detection rates and symptomatic ratios of infected persons. We investigated the appropriate timing for changing the degree of behavioral restrictions and confirmed that early initiating behavioral restrictions is a reasonable measure to reduce the burden on the health care system. We also examined the trade-off between reducing the cumulative number of deaths by the COVID-19 and saving the cost to prevent the spread of the virus. We concluded that a bang-bang control of the behavioral restriction can reduce the socio-economic cost, while a control of the restrictions with multiple levels can reduce the cumulative number of deaths by infection.

Simulating potential outbreaks of Delta and Omicron variants based on contact-tracing data: A modelling study in Fujian Province, China

Although studies have compared the relative severity of Omicron and Delta variants by assessing the relative risks, there are still gaps in the knowledge of the potential COVID-19 burden these variations may cause. And the contact patterns in Fujian Province, China, have not been described. We identified 8969 transmission pairs in Fujian, China, by analyzing a contact-tracing database that recorded a SARS-CoV-2 outbreak in September 2021. We estimated the waning vaccine effectiveness against Delta variant infection, contact patterns, and epidemiology distributions, then simulated potential outbreaks of Delta and Omicron variants using a multi-group mathematical model. For instance, in the contact setting without stringent lockdowns, we estimated that in a potential Omicron wave, only 4.7% of infections would occur in Fujian Province among individuals aged >60 years. In comparison, 58.75% of the death toll would occur in unvaccinated individuals aged >60 years. Compared with no strict lockdowns, combining school or factory closure alone reduced cumulative deaths of Delta and Omicron by 28.5% and 6.1%, respectively. In conclusion, this study validates the need for continuous mass immunization, especially among elderly aged over 60 years old. And it confirms that the effect of lockdowns alone in reducing infections or deaths is minimal. However, these measurements will still contribute to lowering peak daily incidence and delaying the epidemic, easing the healthcare system's burden.

Uncertainty quantification in mechanistic epidemic models via cross-entropy approximate Bayesian computation

This paper proposes a data-driven approximate Bayesian computation framework for parameter estimation and uncertainty quantification of epidemic models, which incorporates two novelties: (i) the identification of the initial conditions by using plausible dynamic states that are compatible with observational data; (ii) learning of an informative prior distribution for the model parameters via the cross-entropy method. The new methodology's effectiveness is illustrated with the aid of actual data from the COVID-19 epidemic in Rio de Janeiro city in Brazil, employing an ordinary differential equation-based model with a generalized SEIR mechanistic structure that includes time-dependent transmission rate, asymptomatics, and hospitalizations. A minimization problem with two cost terms (number of hospitalizations and deaths) is formulated, and twelve parameters are identified. The calibrated model provides a consistent description of the available data, able to extrapolate forecasts over a few weeks, making the proposed methodology very appealing for real-time epidemic modeling.

Modelling Aotearoa New Zealand's COVID-19 protection framework and the transition away from the elimination strategy

For the first 18 months of the COVID-19 pandemic, New Zealand used an elimination strategy to suppress community transmission of SARS-CoV-2 to zero or very low levels. In late 2021, high vaccine coverage enabled the country to transition away from the elimination strategy to a mitigation strategy. However, given negligible levels of immunity from prior infection, this required careful planning and an effective public health response to avoid uncontrolled outbreaks and unmanageable health impacts. Here, we develop an age-structured model for the Delta variant of SARS-CoV-2 including the effects of vaccination, case isolation, contact tracing, border controls and population-wide control measures. We use this model to investigate how epidemic trajectories may respond to different control strategies, and to explore trade-offs between restrictions in the community and restrictions at the border. We find that a low case tolerance strategy, with a quick change to stricter public health measures in response to increasing cases, reduced the health burden by a factor of three relative to a high tolerance strategy, but almost tripled the time spent in national lockdowns. Increasing the number of border arrivals was found to have a negligible effect on health burden once high vaccination rates were achieved and community transmission was widespread.

Clinical performance evaluation of BD SARS-CoV-2 reagents for BD MAXTM System in asymptomatic individuals

Transmission by asymptomatic individuals is a persistent hurdle in the effort to control the spread of SARS-CoV-2. Therefore, it is essential to continue developing assays and evaluate their performance for detection of SARS-CoV-2 in individuals without COVID-19 symptoms. In this study, 223 nasopharyngeal swab specimens collected from COVID-19 asymptomatic individuals were tested using the BD SARS-CoV-2 (RT-PCR-based) reagents for the BD MAX™ System and compared with results obtained with the Biomerieux BioFire® Respiratory RT-PCR Panel. Positive and negative percent agreements of 100% (95% CI, 84.5%-100%) and 99.0% (95% CI, 96.5%-99.7%), respectively, were observed for the BD SARS-CoV-2 assay. These results demonstrate the effectiveness of the BD SARS-CoV-2 assay for detecting SARS-CoV-2 in asymptomatic individuals and suggest that this assay can facilitate optimized case surveillance and infection control efforts. Investigations using larger sample sizes of asymptomatic individuals would be beneficial to support the findings in this study.

Analysis of COVID-19 in Japan with extended SEIR model and ensemble Kalman filter

We introduce an extended SEIR infectious disease model with data assimilation for the study of the spread of COVID-19. In this framework, undetected asymptomatic and pre-symptomatic cases are taken into account, and the impact of their uncertain proportion is fully investigated. The standard SEIR model does not consider these populations, while their role in the propagation of the disease is acknowledged. An ensemble Kalman filter is implemented to assimilate reliable observations of three compartments in the model. The system tracks the evolution of the effective reproduction number and estimates the unobservable subpopulations. The analysis is carried out for three main prefectures of Japan and for the entire country of Japan. For these four communities, our estimated effective reproduction numbers are more stable than the corresponding ones estimated by a different method (Toyokeizai). We also perform sensitivity tests for different values of some uncertain medical parameters, like the relative infectivity of symptomatic/asymptomatic cases. The regional analysis results suggest the decreasing efficiency of the states of emergency.

HLA-A*01:01 allele diminishing in COVID-19 patients population associated with non-structural epitope abundance in CD8+ T-cell repertoire

In mid-2021, the SARS-CoV-2 Delta variant caused the third wave of the COVID-19 pandemic in several countries worldwide. The pivotal studies were aimed at studying changes in the efficiency of neutralizing antibodies to the spike protein. However, much less attention was paid to the T-cell response and the presentation of virus peptides by MHC-I molecules. In this study, we compared the features of the HLA-I genotype in symptomatic patients with COVID-19 in the first and third waves of the pandemic. As a result, we could identify the diminishing of carriers of the HLA-A*01:01 allele in the third wave and demonstrate the unique properties of this allele. Thus, HLA-A*01:01-binding immunoprevalent epitopes are mostly derived from ORF1ab. A set of epitopes from ORF1ab was tested, and their high immunogenicity was confirmed. Moreover, analysis of the results of single-cell phenotyping of T-cells in recovered patients showed that the predominant phenotype in HLA-A*01:01 carriers is central memory T-cells. The predominance of T-lymphocytes of this phenotype may contribute to forming long-term T-cell immunity in carriers of this allele. Our results can be the basis for highly effective vaccines based on ORF1ab peptides.

Influence of Public Sports Services on Residents' Mental Health at Communities Level: New Insights from China

It is generally believed that sports play an important role in healing and boosting mental health. The provision of public sports services is important for enhancing residents' physical fitness and mental health, and for promoting their satisfaction with government public services. To build and strengthen a high-quality sports service-oriented society, it is important to explore whether community public sports services influence residents' mental health. To explore this phenomenon, the study gathered data from China and employed multi-level regression models to meet the study objective. The results show that the residents' age difference is 0.03, and the average daily exercise time is 0.02, which is significantly correlated with residents' mental health. The results show that the lower the availability and greening of sports facilities, and the fewer rest facilities there are, the higher the mental distress of residents may be. Conversely, the improvement of the greening and availability of sports facilities can facilitate the promotion of residents' mental health levels. Moreover, it was found that the mental health of residents is mainly and positively affected by the cleanliness of sports facilities. The street environment affects mental health and is attributed to the damage to sports facilities. Neighborhood communication also improves residents' mental health, and trust between neighbors has the greatest impact on reducing mental distress. Finally, the study proposes that the government should propose strategies to optimize the provision of community public sports services in the study area to boost both social and mental health benefits.

Incidence and risk factors of SARS-CoV-2 infection among workers in a public health laboratory in Tunisia

The aim of this study was to measure the extent of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection among workers at the Institut Pasteur de Tunis (IPT), a public health laboratory involved in the management of the COVID-19 pandemic in Tunisia, and to identify risk factors for infection in this occupational setting. A cross-sectional survey was conducted on IPT workers not vaccinated against coronavirus disease 2019 (COVID-19). Participants completed a questionnaire that included a history of reverse transcription-polymerase chain reaction (RT-PCR)-confirmed SARS-CoV-2 infection. Immunoglobulin G antibodies against the receptor-binding domain of the spike antigen (anti-S-RBD IgG) and the nucleocapsid protein (anti-N IgG) of the SARS-CoV-2 virus were detected by enzyme-linked immunoassay (ELISA). A multivariate analysis was used to identify factors significantly associated with SARS-CoV-2 infection. A total of 428 workers were enrolled in the study. The prevalence of anti-S-RBD and/or anti-N IgG antibodies was 32.9% [28.7-37.4]. The cumulative incidence of SARS-CoV-2 infection (positive serology and/or previous positive RT-PCR test) was 40.0% [35.5-44.9], while the proportion with asymptomatic infection was 32.9%. One-third of the participants with RT-PCR-confirmed infection tested seronegative more than 90 days postinfection. Participants aged over 40 and laborers were more susceptible to infection (adjusted OR [AOR] = 1.65 [1.08-2.51] and AOR = 2.67 [1.45-4.89], respectively), while tobacco smokers had a lower risk of infection (AOR = 0.54 [0.29-0.97]). The SARS-CoV-2 infection rate among IPT workers was not significantly different from that detected concurrently in the general population. Hence, the professional activities conducted in this public health laboratory did not generate additional risk to that incurred outside the institute in day-to-day activities.

Wastewater-based monitoring of SARS-CoV-2 at UK airports and its potential role in international public health surveillance

It is well established that air travel plays a key role in the global spread of many enteric and respiratory diseases, including COVID-19. Even with travel restrictions (e.g. mask wearing, negative COVID-19 test prior to departure), SARS-CoV-2 may be transmitted by asymptomatic or pre-symptomatic individuals carrying the virus. Due to the limitation of current clinical surveillance approaches, complementary methods need to be developed to allow estimation of the frequency of SARS-CoV-2 entry across international borders. Wastewater-based epidemiology (WBE) represents one such approach, allowing the unbiased sampling of SARS-CoV-2 carriage by passenger cohorts entering via airports. In this study, we monitored sewage in samples from terminals (n = 150) and aircraft (n = 32) at three major international airports in the UK for 1-3 weeks in March 2022. As the raw samples were more turbid than typical municipal wastewater, we used beef extract treatment followed by polyethylene glycol (PEG) precipitation to concentrate viruses, followed by reverse transcription quantitative PCR (RT-qPCR) for the detection of SARS-CoV-2 and a faecal indicator virus, crAssphage. All samples taken from sewers at the arrival terminals of Heathrow and Bristol airports, and 85% of samples taken from sites at Edinburgh airport, were positive for SARS-CoV-2. This suggests a high COVID-19 prevalence among passengers and/or airport staff members. Samples derived from aircraft also showed 93% SARS-CoV-2 positivity. No difference in viral prevalence was found before and after COVID-19 travel restrictions were lifted. Our results suggest that WBE is a useful tool for monitoring the global transfer rate of human pathogens and other disease-causing agents across international borders and should form part of wider international efforts to monitor and contain the spread of future disease outbreaks.

Symptomatic and Asymptomatic SARS-CoV-2 Infection and Follow-up of Neutralizing Antibody Levels

OBJECTIVE

To investigate neutralizing antibody levels in symptomatic and asymptomatic patients with coronavirus disease 2019 (COVID-19) at 6 and 10 months after disease onset.

METHODS

Blood samples were collected at three different time points from 27 asymptomatic individuals and 69 symptomatic patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Virus-neutralizing antibody titers against SARS-CoV-2 in both groups were measured and statistically analyzed.

RESULTS

The symptomatic and asymptomatic groups had higher neutralizing antibodies at 3 months and 1-2 months post polymerase chain reaction confirmation, respectively. However, neutralizing antibodies in both groups dropped significantly to lower levels at 6 months post-PCR confirmation.

CONCLUSION

Continued monitoring of symptomatic and asymptomatic individuals with COVID-19 is key to controlling the infection.

Evidence synthesis, digital scribes, and translational challenges for artificial intelligence in healthcare

Healthcare has well-known challenges with safety, quality, and effectiveness, and many see artificial intelligence (AI) as essential to any solution. Emerging applications include the automated synthesis of best-practice research evidence including systematic reviews, which would ultimately see all clinical trial data published in a computational form for immediate synthesis. Digital scribes embed themselves in the process of care to detect, record, and summarize events and conversations for the electronic record. However, three persistent translational challenges must be addressed before AI is widely deployed. First, little effort is spent replicating AI trials, exposing patients to risks of methodological error and biases. Next, there is little reporting of patient harms from trials. Finally, AI built using machine learning may perform less effectively in different clinical settings.

Impact of Personal Experience of COVID-19 Disease on Recreational Anglers' Attitudes and Behaviors

BACKGROUND

Anglers are a large social group with access to a "relatively safe" form of recreation, that allows the opportunity to relieve stress. An important question, however, is how they did so, and to what extent their perceived COVID-19 transition status influenced decisions both in life and at the fishing site.

AIM

Our study aimed to determine the dynamics of anglers' attitudes and behaviors during the COVID-19 pandemic as a result of the different statuses of their exposure to the SARS-CoV-2 virus. We assumed that the behavior of anglers who have not experienced the disease (were not ill and not sure if ill) will be similar and, on the other hand, different from the behavior of those who have experienced COVID-19.

METHODS

The web-assisted interviews survey was used among 586 anglers with different COVID-19 disease experience statuses. Their pandemic behavior and activities by four age groups were studied using non-metric multidimensional scaling. Redundancy analysis has been used to identify the relationship between anglers' life attitudes and socioeconomic and demographic factors, taking into account their preferences and involvement in fishing.

RESULTS

We have demonstrated that the behavior of anglers who have not experienced COVID-19 disease and do not present a reckless attitude toward pandemic threats, do not show significant differences from the life attitudes of the group experienced by the SARS-CoV-2 virus. These two groups comprise more than 70% of anglers. However, the rest show a lack of interest in an aware diagnosis of their health and a low level of acceptance of self-restraint in the area of direct social contact.

CONCLUSIONS

Unawareness, combined with ignorance, could be a potential factor in the transmission of the virus while fishing. The behaviors of almost 30% of anglers are particularly risky when combined with a strong need to fish in the company of friends and familiar people. Anglers' social identity should be tapped by fishery managers. Targeted educational campaigns should be aimed at groups around specific fishing spots. The need for self-limitation under the pandemic should be promoted for the benefit of the general public and to maintain the reputation of angling as a safe recreational activity.

Understanding the impact of digital contact tracing during the COVID-19 pandemic

Digital contact tracing (DCT) applications have been introduced in many countries to aid the containment of COVID-19 outbreaks. Initially, enthusiasm was high regarding their implementation as a non-pharmaceutical intervention (NPI). However, no country was able to prevent larger outbreaks without falling back to harsher NPIs. Here, we discuss results of a stochastic infectious-disease model that provide insights in how the progression of an outbreak and key parameters such as detection probability, app participation and its distribution, as well as engagement of users impact DCT efficacy informed by results of empirical studies. We further show how contact heterogeneity and local contact clustering impact the intervention's efficacy. We conclude that DCT apps might have prevented cases on the order of single-digit percentages during single outbreaks for empirically plausible ranges of parameters, ignoring that a substantial part of these contacts would have been identified by manual contact tracing. This result is generally robust against changes in network topology with exceptions for homogeneous-degree, locally-clustered contact networks, on which the intervention prevents more infections. An improvement of efficacy is similarly observed when app participation is highly clustered. We find that DCT typically averts more cases during the super-critical phase of an epidemic when case counts are rising and the measured efficacy therefore depends on the time of evaluation.

Sauver J. Rates of Asymptomatic COVID-19 Infection and Associated Factors in Olmsted County, Minnesota, in the Prevaccination Era

Objective

To estimate rates and identify factors associated with asymptomatic COVID-19 in the population of Olmsted County during the prevaccination era.

Patients and Methods

We screened first responders (n=191) and Olmsted County employees (n=564) for antibodies to SARS-CoV-2 from November 1, 2020 to February 28, 2021 to estimate seroprevalence and asymptomatic infection. Second, we retrieved all polymerase chain reaction (PCR)-confirmed COVID-19 diagnoses in Olmsted County from March 2020 through January 2021, abstracted symptom information, estimated rates of asymptomatic infection and examined related factors.

Results

Twenty (10.5%; 95% CI, 6.9%-15.6%) first responders and 38 (6.7%; 95% CI, 5.0%-9.1%) county employees had positive antibodies; an additional 5 (2.6%) and 10 (1.8%) had prior positive PCR tests per self-report or medical record, but no antibodies detected. Of persons with symptom information, 4 of 20 (20%; 95% CI, 3.0%-37.0%) first responders and 10 of 39 (26%; 95% CI, 12.6%-40.0%) county employees were asymptomatic. Of 6020 positive PCR tests in Olmsted County with symptom information between March 1, 2020, and January 31, 2021, 6% (n=385; 95% CI, 5.8%-7.1%) were asymptomatic. Factors associated with asymptomatic disease included age (0-18 years [odds ratio {OR}, 2.3; 95% CI, 1.7-3.1] and >65 years [OR, 1.40; 95% CI, 1.0-2.0] compared with ages 19-44 years), body mass index (overweight [OR, 0.58; 95% CI, 0.44-0.77] or obese [OR, 0.48; 95% CI, 0.57-0.62] compared with normal or underweight) and tests after November 20, 2020 ([OR, 1.35; 95% CI, 1.13-1.71] compared with prior dates).

Conclusion

Asymptomatic rates in Olmsted County before COVID-19 vaccine rollout ranged from 6% to 25%, and younger age, normal weight, and later tests dates were associated with asymptomatic infection.

An Analysis of SARS-CoV-2 in Wastewater to Evaluate the Effectiveness of Nonpharmaceutical Interventions against COVID-19 in The Netherlands

Wastewater-based epidemiology (WBE) is increasingly being recognized as a powerful tool for detecting and monitoring SARS-CoV-2 trends at a population level. This study looked to extend the use of WBE to explore the effectiveness of nonpharmaceutical interventions (NPIs) that have been used in response to COVID-19 and compare the results to the effect of such interventions on COVID-19 hospitalizations. A data-driven approach demonstrated that trends of SARS-CoV-2 RNA in wastewater, from Amsterdam and Utrecht (The Netherlands), precede hospitalizations by at least 3-9 days. Additionally, the effect of NPIs can be seen in wastewater and hospitalizations after 20 and 24 days, respectively. Changepoint analysis indicated that the closure of schools and universities significantly reduced the level of SARS-CoV-2 RNA in wastewater and COVID-19 hospitalizations. Regression modeling suggested the stay-at-home policy is an effective intervention for reducing the level of SARS-CoV-2 RNA in wastewater, whereas the closure of workplaces significantly reduced hospitalizations in both Dutch cities. This study demonstrates how WBE can be used to inform public health decisions and anticipate future strain on healthcare facilities in major cities but also indicates a need for higher temporal resolution of wastewater sampling.

Lower transmissibility of SARS-CoV-2 among asymptomatic cases: evidence from contact tracing data in Oslo, Norway

BACKGROUND

Asymptomatic COVID-19 cases have complicated the surveillance and tracking of the pandemic. Previous studies have estimated that 15-25% of all infectees remain asymptomatic.

METHODS

Based on contact tracing data from Oslo, Norway, we estimated transmission and susceptibility dynamics among symptomatic and asymptomatic cases and their contacts as identified by manual contact tracing between September 1, 2020, and September 1, 2021.

RESULTS

Among 27,473 indexes and 164,153 registered contacts, the secondary attack rate (SAR-14) was estimated to be 28% lower through asymptomatic exposure (13%) compared to symptomatic exposure (18%). Furthermore, those infected by asymptomatic cases were almost three times more likely to be asymptomatic compared to those infected by symptomatic cases.

CONCLUSIONS

Symptomatic cases spread the virus to a greater extent than asymptomatic, and infectees are more likely to be asymptomatic if their assumed infector was asymptomatic.

Risk-based decision-making related to preprocedural coronavirus disease 2019 testing in the setting of GI endoscopy: management of risks, evidence, and behavioral health economics

BACKGROUND AND AIMS

Controversies exist regarding the benefits and most appropriate approach for preprocedural coronavirus disease 2019 (COVID-19) testing (eg, rapid antigen test, polymerase chain reaction, or real-time polymerase chain reaction) for outpatients undergoing diagnostic and therapeutic procedures, such as GI endoscopy, to prevent COVID-19 infections among staff. Guidelines for protecting healthcare workers (HCWs) from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection from outpatient procedures varies across medical professional organizations. This study provides an evidence-based decision support tool for key decision-makers (eg, clinicians) to respond to COVID-19 transmission risks and reduce the effect of personal biases.

METHODS

A scoping review was used to identify relevant factors influencing COVID-19 transmission risk relevant for GI endoscopy. From 12 relevant publications, 8 factors were applicable: test sensitivity, prevalence of SARS-CoV-2 in the population, age-adjusted SARS-CoV-2 prevalence in the patient cohort, proportion of asymptomatic patients, risk of transmission from asymptomatic carriers, risk reduction by personal protective equipment (PPE), vaccination rates of HCWs, and risk reduction of SAE by vaccination. The probability of a serious adverse event (SAE), such as workplace-acquired infection resulting in HCW death, under various scenarios with preprocedural testing was determined to inform decision-makers of expected costs of reductions in SAEs.

RESULTS

In a setting of high community transmission, without testing and PPE, 117.5 SAEs per million procedures were estimated to occur, and this was reduced to between .079 and 2.35 SAEs per million procedures with the use of PPE and preprocedural testing. When these variables are used and a range of scenarios are tested, the probability of an SAE was low even without testing but was reduced by preprocedural testing.

CONCLUSIONS

Under all scenarios tested, preprocedural testing reduced the SAE risk for HCWs regardless of the SARS-CoV-2 variant. Benefits of preprocedural testing are marginal when community transmission is low (eg, below 10 infections a day per 100,000 population). The proposed decision support tool can assist in developing rational preprocedural testing policies.

Epidemiologic information discovery from open-access COVID-19 case reports via pretrained language model

Although open-access data are increasingly common and useful to epidemiological research, the curation of such datasets is resource-intensive and time-consuming. Despite the existence of a major source of COVID-19 data, the regularly disclosed case reports were often written in natural language with an unstructured format. Here, we propose a computational framework that can automatically extract epidemiological information from open-access COVID-19 case reports. We develop this framework by coupling a language model developed using deep neural networks with training samples compiled using an optimized data annotation strategy. When applied to the COVID-19 case reports collected from mainland China, our framework outperforms all other state-of-the-art deep learning models. The information extracted from our approach is highly consistent with that obtained from the gold-standard manual coding, with a matching rate of 80%. To disseminate our algorithm, we provide an open-access online platform that is able to estimate key epidemiological statistics in real time, with much less effort for data curation.

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We propose a method to obtain epidemiological information from COVID-19 case reports

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The extracted information has 80% matching rate with the gold-standard manual coding

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Normal lark, deviant owl: The relationship between chronotype and compliance with COVID-19 mitigation measures

Current evidence suggests that preventive measures, such as social distancing and wearing face masks, are critical to contain the spread of COVID-19. The recent burgeoning literature has empirically examined how a wide range of facet-level personality and individual-differences variables are associated with people's adherence to COVID-19 regulations. However, there lacks direct evidence regarding the role of chronotype in compliance with pandemic safety measures. According to the eveningness epidemiological liability hypothesis, people of later chronotype are more likely to breach COVID-19 restrictions. Despite this hypothesis shedding considerable light on the potential role of chronotype in the abidance of the virus-mitigating measures, it has not been rigorously tested using empirical data. To fill this gap, the present research investigated the link between morningness-eveningness and compliance with COVID-19 containment policies in Chinese samples. Two studies using multiple populations (students and community adults) and diverse measures of adherence to public health guidelines (self-report and actual behavior) consistently show that individuals who orient towards morningness display a higher level of compliance with COVID-19 prevention than people who orient towards eveningness. Overall, these findings present the first empirical confirmation of the eveningness epidemiological liability hypothesis, highlighting the role of chronotype in adherence to COVID-19 prevention guidelines.

Effect of asymptomatic transmission and emergence time on multi-strain viral disease severity

In a viral epidemic, the emergence of a novel strain with increased transmissibility (larger value of basic reproduction number R₀) sparks the fear that the increase in transmissibility is likely to lead to an increase in disease severity. It is required to investigate if a new, more contagious strain will be necessarily dominant in the population and resulting in more disease severity. In this paper, the impact of the asymptomatic transmission and the emergence time of a more transmissible variant of a multi-strain viral disease on the disease prevalence, disease severity, and the dominant variant in an epidemic was investigated by a proposed 2-strain epidemic model. The simulation results showed that considering only R₀, is insufficient to predict the outcome of a new, more contagious strain in the population. A more transmissible strain with a high fraction of asymptomatic cases can substantially reduce the mortality rate. If the emergence time of the new strain is closer to the start of the epidemic, the new, more contagious variant has more chance to win the viral competition and be the dominant strain; otherwise, despite being more contagious, it cannot dominate previous strains. In conclusion, three factors of R₀, the fraction of asymptomatic transmission, and the emergence time of the new strain are required to correctly determine the prevalence, disease severity, and the winner of the viral competition.

Household transmission of the Delta COVID-19 variant in Queensland, Australia: a case series

Household transmission plays a key role in the spread of COVID-19 through populations. In this paper, we report on the transmission of COVID-19 within households in a metropolitan area in Australia, examine the impact of various factors and highlight priority areas for future public health responses. We collected and reviewed retrospective case report data and follow-up interview responses from households with a positive case of the Delta COVID-19 variant in Queensland in 2021. The overall secondary attack rate (SAR) among household contacts was 29.6% and the mean incubation period for secondary cases was 4.3 days. SAR was higher where the index case was male (57.9% vs. 14.3%) or aged ≤12 years (38.7% vs. 17.4%) but similar for adult contacts that were double vaccinated (35.7%) and unvaccinated (33.3%). Most interview participants emphasised the importance of clear, consistent and compassionate health advice as a key priority for managing outbreaks in the home. The overall rate of household transmission was slightly higher than that reported in previous studies on the wild COVID-19 variant and secondary infections developed more rapidly. While vaccination did not appear to affect the risk of transmission to adult subjects, uptake in the sample was ultimately high.

Clinical Profiles at the Time of Diagnosis of SARS-CoV-2 Infection in Costa Rica During the Pre-vaccination Period Using a Machine Learning Approach

The clinical manifestations of COVID-19, caused by the SARS-CoV-2, define a large spectrum of symptoms that are mainly dependent on the human host conditions. In Costa Rica, more than 169,000 cases and 2185 deaths were reported during the year 2020, the pre-vaccination period. To describe the clinical presentations at the time of diagnosis of SARS-CoV-2 infection in Costa Rica during the pre-vaccination period, we implemented a symptom-based clustering using machine learning to identify clusters or clinical profiles at the population level among 18,974 records of positive cases. Profiles were compared based on symptoms, risk factors, viral load, and genomic features of the SARS-CoV-2 sequence. A total of 18 symptoms at time of diagnosis of SARS-CoV-2 infection were reported with a frequency > 1%, and those were used to identify seven clinical profiles with a specific composition of clinical manifestations. In the comparison between clusters, a lower viral load was found for the asymptomatic group, while the risk factors and the SARS-CoV-2 genomic features were distributed among all the clusters. No other distribution patterns were found for age, sex, vital status, and hospitalization. In conclusion, during the pre-vaccination time in Costa Rica, the symptoms at the time of diagnosis of SARS-CoV-2 infection were described in clinical profiles. The host co-morbidities and the SARS-CoV-2 genotypes are not specific of a particular profile, rather they are present in all the groups, including asymptomatic cases. In addition, this information can be used for decision-making by the local healthcare institutions (first point of contact with health professionals, case definition, or infrastructure). In further analyses, these results will be compared against the profiles of cases during the vaccination period.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s43657-022-00058-x.

Data-driven approach in a compartmental epidemic model to assess undocumented infections

Nowcasting and forecasting of epidemic spreading rely on incidence series of reported cases to derive the fundamental epidemiological parameters for a given pathogen. Two relevant drawbacks for predictions are the unknown fractions of undocumented cases and levels of nonpharmacological interventions, which span highly heterogeneously across different places and times. We describe a simple data-driven approach using a compartmental model including asymptomatic and pre-symptomatic contagions that allows to estimate both the level of undocumented infections and the value of effective reproductive number R t from time series of reported cases, deaths, and epidemiological parameters. The method was applied to epidemic series for COVID-19 across different municipalities in Brazil allowing to estimate the heterogeneity level of under-reporting across different places. The reproductive number derived within the current framework is little sensitive to both diagnosis and infection rates during the asymptomatic states. The methods described here can be extended to more general cases if data is available and adapted to other epidemiological approaches and surveillance data.

Quantifying the dynamic transmission of COVID-19 asymptomatic and symptomatic infections: Evidence from four Chinese regions

The dynamic transmission of asymptomatic and symptomatic COVID-19 infections is difficult to quantify because asymptomatic infections are not readily recognized or self-identified. To address this issue, we collected data on asymptomatic and symptomatic infections from four Chinese regions (Beijing, Dalian, Xinjiang, and Guangzhou). These data were considered reliable because the government had implemented large-scale multiple testing during the outbreak in the four regions. We modified the classical susceptible-exposure-infection-recovery model and combined it with mathematical tools to quantitatively analyze the number of infections caused by asymptomatic and symptomatic infections during dynamic transmission, respectively. The results indicated that the ratios of the total number of asymptomatic to symptomatic infections were 0.13:1, 0.48:1, 0.29:1, and 0.15:1, respectively, in the four regions. However, the ratio of the total number of infections caused by asymptomatic and symptomatic infections were 4.64:1, 6.21:1, 1.49:1, and 1.76:1, respectively. Furthermore, the present study describes the daily number of healthy people infected by symptomatic and asymptomatic transmission and the dynamic transmission process. Although there were fewer asymptomatic infections in the four aforementioned regions, their infectivity was found to be significantly higher, implying a greater need for timely screening and control of infections, particularly asymptomatic ones, to contain the spread of COVID-19.