COVID-19 outbreak among employees of a German hospital – risk factor analysis based on a follow-up questionnaire and seroprevalence

Abstract

Abstract The Co-FriSero study (COVID-Friedrichroda seroprevalence study) describes a COVID-19 outbreak in a German hospital with 185 beds (Friedrichroda/Thuringia) and 404 employees at the beginning of the pandemics, which was followed up with a questionnaire and seroprevalence study of the entire hospital staff. Seroprevalence was assessed using two different immunoassays to detect IgG and a third different immunoassay in those with discordant results. Between March 30th 2020 and April 13th 2020, a COVID-19 outbreak occurred within the hospital staff. SARS-CoV-2 infection was confirmed in 25 of 229 employees screened by PCR and in 7 employees by serology only. Employee-reported compliance with wearing personal protective equipment (PPE) differed between those working in the high-risk area (80%) and those in the medium-risk area (72%). Statistical analysis of risk factors revealed an association between SARS-CoV-2 infection and the following potential sources of infection: direct patient contact, exposure to patients with high flow ventilation through unclosed room doors, direct contact with colleagues, lounge, and carpooling among staff. No direct link to infection was represented by contact with family and friends, or public transportation, visiting public events and using health care worker locker rooms. This study underscores that during the early stages of the pandemic, direct patient contact, particularly with ventilated patients through open doors, and inadequate hygiene measures increased the risk for health care workers. Additionally, the study suggests that once introduced, the pathogen can spread outside the hospital setting via staff interactions, emphasizing the need to consider previously overlooked transmission routes, such as carpooling, in future pandemic planning.