The social distancing guidance is based on outdated science and should reflect the multiple factors that affect transmission risk according to a new review published by researchers at Oxford University.
The notion that either keeping either 1 or 2m apart is sufficient to reduce transmission of the virus, overlooks the physics of respiratory emissions which depends on a number of factors including the viral load of the emitter, duration of exposure and an individual’s susceptibility to infection.
The authors cite evidence from recent studies which have indicated how COVID-19 can persist in airborne samples for up to 16 hours and that breathing out, singing coughing and sneezing generate warm, moist high momentum gas clouds that can extend much further than 2m and up to 8m in a few seconds. The authors offer a guide to how the risk of transmission from an asymptomatic individual varies in different settings and for different exposure times and call for more research to establish solutions to indoor environments at varying levels of occupancy.
Airflow patterns within building are an equally important contributors to the risk of transmission, as evidenced from a Chinese restaurant study in which infection occurred over a distance of 4.6m in the space of an hour without physical contact.
The authors conclude that physical distancing should be viewed as only one aspect of an overall strategy that considers people-air-surface-space management, occupancy levels, air management and appropriate use of masks for a given setting.
Jones NR et al. Two metres or one: what is the evidence for physical distancing in Covid-19? BMJ 2020;370:m3223 http://dx.doi.org/10.1136/bmj.m3223