Knowledge of the period of high infectiousness is particularly useful in the context of contact tracing as it allows to identify the contacts at highest risk of having contracted the disease, maximising the number of infectious individuals in quarantine while minimising the number of people unnecessarily isolated. The preprint paper 'The timing of Covid-19 transmission', published in MedRxiv, is centered around the question “When is someone who has been infected with COVID-19 most likely to infect others?”.
The analysis focuses on individuals who eventually develop symptoms, studying 191 transmission pairs from multiple data sets. Each transmission pair includes an index case and a secondary case, infected by the index case. Datasets were selected because they contained information not only about the dates of onset of symptoms for both cases, but also intervals of exposure for the index and/or secondary case. For these pairs and individuals, four key timings related to Covid-19 transmission were known or inferred.