Societal Activities Associated With SARS-CoV-2 Infection – A Case-Control Study in Denmark, November 2020

Abstract

Background: Quantifying the risk of infection with SARS-CoV-2 associated with community exposures, may provide an evidence base for implementing preventive measures. Here, we investigated potential determinants for infection in Denmark in a situation where society was only partially open.

Methods: We conducted a national matched case-control study. Cases were recent RT-PCR test-positives, while controls, individually matched on age, sex and residence, had not previously tested positive for SARS-CoV-2. Questions concerned person contact and community exposures. Telephone interviews were performed over a seven-day period in December 2020. We included 300 cases and 317 controls and determined odds ratios (ORs) and 95% confidence intervals (95%CI) by conditional logistical regression with adjustment for household size and country of origin.

Findings: Contact (OR=4·9,95%CI:2·4-10), and close contact (OR=13, 95%CI:6·7-25), with a person with a known SARS-CoV-2 infection were main determinants. Contact most often took place in the household or work place. Community determinants included: events with singing (OR=2.1, 95%CI:1·1-4·1), attending fitness centre (OR=1·8, 95%CI:1·1-2·8) and consumption of alcohol in a bar (OR=10, 95%CI:1·5-65). Other community exposures appeared not to be associated with infection, these included shopping at supermarkets, travel by public transport, dining at restaurants and private social events with few participants.

Interpretations: Events with singing and fitness centres were associated with transmission risks. Other than that, the restrictions in place at the time of the study appeared to be sufficient to reduce transmission of disease in the public space, which instead took place following direct exposures to people with known SARS-CoV-2 infections.

Funding Information: None.

Declaration of Interests: All authors have nothing to declare.

Ethics Approval Statement: The study was performed as a national disease surveillance project, registered with the Danish Data Protection Agency (reg no 20/10133) and approved regarding legal, ethical and cyber-security issues. Participation was voluntary and participants received information about the selection procedure, risks associated with participation, data security, legal rights, including the right to withdraw from the study, and the use of their information at the start of the interview. The collaboration with the polling company was regulated by a data processing agreement and carried out on commercial terms.