Social contact patterns during the early COVID-19 pandemic in Norway: insights from a panel study, April to September 2020 (preprint)

BackgroundDuring the COVID-19 pandemic, many countries adopted social distance measures and lockdowns of varying strictness. Social contact patterns are essential in driving the spread of respiratory infections, and country-specific measurements are needed. This study aimed to gain insights into changes in social contacts and behaviour during the early pandemic phase in Norway. MethodsWe conducted an online survey among a nationally representative sample of Norwegian adults, including six data collections/waves between April and September 2020, and used survey data from 2017 as baseline. We calculated mean daily contacts, and estimated age-stratified contact matrices that were used to estimate reproduction numbers during the study period. ResultsThe mean daily number of contacts varied between 3.2 (95% CI 3.0-3.4) to 3.9 (95% CI 3.6-4.2) across waves, representing a 67-73% decline compared to pre-pandemic levels. Fewer contacts in the community setting largely drove the reduction; the drop was most prominent among younger adults. Despite gradual easing of social distance measures during the survey period, population contact matrices remained relatively stable and displayed more inter-age group mixing than at baseline. Contacts within households and the community outside schools and workplaces contributed most to social encounters. ConclusionSocial contacts experienced a significant decline during the months following the March 2020 lockdown in Norway, aligning with the implementation of stringent social distancing measures. The findings contribute valuable empirical information into the social behaviour of the Norwegian population during the early pandemic, which can be used to enhance policy-relevant models for addressing future crises when mitigation measures might be implemented.

The influence of risk perceptions on close contact frequency during the SARS-CoV-2 pandemic (preprint)

Human behaviour is known to be crucial in the propagation of infectious diseases through respiratory or close-contact routes like the current SARS-CoV-2 virus. Intervention measures implemented to curb the spread of the virus mainly aim at limiting the number of close contacts, until vaccine roll-out is complete. Our main objective was to assess the relationships between SARS-CoV-2 perceptions and social contact behaviour in Belgium. Understanding these relationships is crucial to maximize interventions' effectiveness, e.g. by tailoring public health communication campaigns. In this study, we surveyed a representative sample of adults in Belgium in two longitudinal surveys (8 waves of survey 1 in April 2020 to August 2020, and 11 waves of survey 2 in November 2020 to April 2021). Generalized linear mixed effects models were used to analyse the two surveys. Participants with low and neutral perceptions on perceived severity made a significantly higher number of social contacts as compared to participants with high levels of perceived severity after controlling for other variables. Furthermore, participants with higher levels of perceived effectiveness of measures and perceived adherence to measures made fewer contacts. However, the differences were small. Our results highlight the key role of perceived severity on social contact behaviour during a pandemic. Nevertheless, additional research is required to investigate the impact of public health communication on severity of COVID-19 in terms of changes in social contact behaviour.

Inferring the number of COVID-19 cases from recently reported deaths (preprint)

We estimate the number of COVID-19 cases from newly reported deaths in a population without previous reports. Our results suggest that by the time a single death occurs, hundreds to thousands of cases are likely to be present in that population. This suggests containment via contact tracing will be challenging at this point, and other response strategies should be considered. Our approach is implemented in a publicly available, user-friendly, online tool.