The ‘circadian clock’ is an inbuilt 24-hour clock recognised in human biology that, along with a seasonal clock (summer/winter), impacts on how environmental challenges are handled, including influencing the outcome of infectious diseases and vaccinations (Borrmann 2020, Sengupta 2021).The COVID-19 pandemic, caused by SARS-CoV-2 coronavirus, is a global crisis with unprecedented challenges for public health. Our laboratory data shows a circadian regulation of SARS-CoV-2 RNA levels that has potential impacts on: [1] SARS-CoV-2 diagnostics; [2] time-dependent shedding of virus, that could influence transmission; [3] epidemiological studies of SARS-CoV-2 ‘contact tracing’. We are therefore setting out first to determine whether the time of sample collection from patients and staff with SARS-CoV-2 infection has any bearing on the amount of virus we can detect in the sample. Second, we will investigate whether the effect of this biological clock is dependent on age or sex, location in the hospital, duration of hospital admission and disease severity.