Seeding of outbreaks of COVID-19 by contaminated fresh and frozen food

The authors have withdrawn this manuscript because some aspects of the published work were completed prior to regulatory approval. Therefore, the authors do not wish this work to be cited as reference for the project. If you have any questions, please contact the corresponding author.

Projecting contact matrices in 177 geographical regions: an update and comparison with empirical data for the COVID-19 era

Mathematical models have played a key role in understanding the spread of directly-transmissible infectious diseases such as Coronavirus Disease 2019 (COVID-19), as well as the effectiveness of public health responses. As the risk of contracting directly-transmitted infections depends on who interacts with whom, mathematical models often use contact matrices to characterise the spread of infectious pathogens. These contact matrices are usually generated from diary-based contact surveys. However, the majority of places in the world do not have representative empirical contact studies, so synthetic contact matrices have been constructed using more widely available setting-specific survey data on household, school, classroom, and workplace composition combined with empirical data on contact patterns in Europe. In 2017, the largest set of synthetic contact matrices to date were published for 152 geographical locations. In this study, we update these matrices with the most recent data and extend our analysis to 177 geographical locations. Due to the observed geographic differences within countries, we also quantify contact patterns in rural and urban settings where data is available. Further, we compare both the 2017 and 2020 synthetic matrices to out-of-sample empirically-constructed contact matrices, and explore the effects of using both the empirical and synthetic contact matrices when modelling physical distancing interventions for the COVID-19 pandemic. We found that the synthetic contact matrices reproduce the main traits of the contact patterns in the empirically-constructed contact matrices. Models parameterised with the empirical and synthetic matrices generated similar findings with few differences observed in age groups where the empirical matrices have missing or aggregated age groups. This finding means that synthetic contact matrices may be used in modelling outbreaks in settings for which empirical studies have yet to be conducted. Author summaryThe risk of contracting a directly transmitted infectious disease such as the Coronavirus Disease 2019 (COVID-19) depends on who interacts with whom. Such person-to-person interactions vary by age and locations--e.g., at home, at work, at school, or in the community--due to the different social structures. These social structures, and thus contact patterns, vary across and within countries. Although social contact patterns can be measured using contact surveys, the majority of countries around the world, particularly low- and middle-income countries, lack nationally representative contact surveys. A simple way to present contact data is to use matrices where the elements represent the rate of contact between subgroups such as age groups represented by the columns and rows. In 2017, we generated age- and location-specific synthetic contact matrices for 152 geographical regions by adapting contact pattern data from eight European countries using country-specific data on household size, school and workplace composition. We have now updated these matrices with the most recent data (Demographic Household Surveys, World Bank, UN Population Division) extending the coverage to 177 geographical locations, covering 97.2% of the worlds population. We also quantified contact patterns in rural and urban settings. When compared to out-of-sample empirically-measured contact patterns, we found that the synthetic matrices reproduce the main features of these contact patterns.

Population anxiety and positive behaviour change during the COVID-19 epidemic: Cross-sectional surveys in Singapore, China and Italy

BackgroundOn 31 December 2019, an epidemic of pneumonia of unknown aetiology was first reported in the city of Wuhan, Hubei Province, Peoples Republic of China. A rapidly progressing epidemic of COVID-19 ensued within China, with multiple exportations to other countries. We aimed to measure perceptions and responses towards COVID-19 in three countries to understand how population-level anxiety can be mitigated in the early phases of a pandemic. MethodsBetween February and March 2020, we conducted online surveys in Singapore, China and Italy with a total of 4,505 respondents to measure respondents knowledge, perceptions, anxiety and behaviours towards the COVID-19 epidemic, and identified factors associated with lower anxiety and more positive behavioural responses. FindingsRespondents reported high awareness of COVID-19 and its accompanying symptoms, comparable information seeking habits and similarly high levels of information sufficiency, adherence to and acceptance of public health control measures. Higher self-efficacy was associated with lower anxiety levels in all three countries, while willingness to comply with restrictive measures and greater information sufficiency were associated with more positive behavioural changes to reduce spread of infection. InterpretationPopulation-level anxiety and behavioural responses to an outbreak can be influenced by information provided. This should be used to inform future outbreak preparedness plans, taking into account the importance of increasing population-level self-efficacy and information sufficiency to reduce anxiety and promote positive behavioural changes. FundingThis was supported by the Saw Swee Hock School of Public Health, the Department of Communications and New Media, National University of Singapore, and the National Medical Research Council, Singapore

Comfort and exertion while using filtering facepiece respirators with exhalation valve and an active venting system among male military personnel

<p><b>INTRODUCTION</b>This study aimed to determine if disposable filtering facepiece respirators (FFRs) that come with an exhalation valve (EV) and a novel active venting system (AVS) provided greater perceived comfort and exertion when compared to standard N95 FFRs without these features among male military personnel performing prolonged essential outdoor duties.</p><p><b>METHODS</b>We used a randomised open-label controlled crossover study design to compare three FFR options: (a) standard FFR; (b) FFR with EV; and (c) FFR with EV+AVS. Male military personnel aged between 18 and 20 years completed a questionnaire at the start of outdoor duty (baseline), after two hours of standardised non-strenuous outdoor duty and after 12 hours of duty divided into two-hour work-rest cycles. Participants rated the degree of discomfort, exertion and symptoms using a five-point Likert scale. The association between outcomes and types of FFR was assessed using a multivariate ordered probit mixed-effects model.</p><p><b>RESULTS</b>For a majority of the symptoms, study participants gave FFR with EV and FFR EV+AVS significantly better scores than standard FFR. Both FFR with EV and FFR with EV+AVS had significantly less discomfort (FFR with EV+AVS: 91.1%; FFR with EV: 57.6%) and exertion (FFR with EV+AVS: 83.5%; FFR with EV: 34.4%) than standard FFR. FFR with EV+AVS also had significantly better scores for exertion (53.4%) and comfort (39.4%) when compared to FFR with EV.</p><p><b>CONCLUSION</b>Usage of FFR with EV+AVS resulted in significantly reduced symptoms, discomfort and exertion when compared to FFR with EV and standard FFR.</p>