Introduction SARS-CoV-2 is a highly transmissible novel virus that has caused the COVID-19 pandemic. Evidence is required to support effective mitigation strategies. Existing evidence has shown that the virus can be transmitted mainly through three routes: close-range airborne (droplets and aerosols), longer range inhalation of aerosol, contact with contaminated surfaces. However, their relative importance is not well understood. It is also unclear how environmental conditions can alter the dynamics of the virus transmission.

Objectives The COVID-OUT (COVID-19 Outbreak investigation to Understand Transmission) study aims to understand SARS-CoV-2 transmission routes, transmission risk factors, and the role they play in COVID-19 outbreak in workplaces.

Methods This study is part of the UK COVID-19 National Core Study (NCS) on Transmission and the Environment. The study has a series of field studies to investigate outbreaks in a range of workplaces. Each field study has serial measurements of workers and measurements in the work environments. Environmental assessment is an essential component of the study. Its data can be combined with epidemiological and laboratory data to generate hypotheses of the causes of an outbreak and can also be used to support simulation models to characterize the relative contribution of transmission routes.

Results So far three outbreak workplaces have been investigated. Preliminary findings and lessons learnt will be presented.

Conclusion The field study data collection is led by a team of occupational hygienists from the Health and Safety Executive (HSE) who work closely with epidemiologists, public health investigators, microbiologists, environmental exposure specialists to ensure critical data are collected and findings are interpreted appropriately. Occupational hygienists are skilled in assessing physical, chemical and biological hazards in workplace settings. They are equipped with established tools and frameworks for assessing risks of various hazards which can be adapted and applied in COVID-19 outbreak investigations.