Two metres or one: what is the evidence for physical distancing in covid-19?

Abstract

Physical distancing is an important part of measures to control covid-19, but exactly how far away and for how long contact is safe in different contexts is unclear. Rules that stipulate a single specific physical distance (1 or 2 metres) between individuals to reduce transmission of SARS-CoV-2, the virus causing covid-19, are based on an outdated, dichotomous notion of respiratory droplet size. This overlooks the physics of respiratory emissions, where droplets of all sizes are trapped and moved by the exhaled moist and hot turbulent gas cloud that keeps them concentrated as it carries them over metres in a few seconds. 1 2 After the cloud slows sufficiently, ventilation, specific patterns of airflow, and type of activity become important. Viral load of the emitter, duration of exposure, and susceptibility of an individual to infection are also important. Instead of single, fixed physical distance rules, we propose graded recommendations that better reflect the multiple factors that combine to determine risk. This would provide greater protection in the highest risk settings but also greater freedom in lower risk settings, potentially enabling a return towards normality in some aspects of social and economic life.

The Effect of the COVID-19 Pandemic on Riding Lesson Barns and Summer Camps in Ontario

“…Physical distancing is another important precaution to prevent the spread of COVID-19, however may be more difficult to implement in barns with narrow aisles or when assisting riding lesson students. The 2 m physical distancing rule was proposed based on studies done in the mid-19th century showing that most droplets produced by sneezing or coughing traveled less than 2 m distance, despite more recent evidence showing droplet spread up to 8 m away [7]. Most riding facilities approached physical distancing by limiting the number of people on the property or limiting access to certain areas of the facility to reduce the opportunities for close contact to other people.…”

Hygiene and social distancing as distinct public health related behaviours among university students during the COVID-19 pandemic

“…Second, studies of health-related behaviours usually focus on one type of behaviour (e.g., smoking or drinking) or a range of closely related behaviours (e.g., eating habits). COVID-19 related recommendations cover more diverse types of behaviours not necessarily closely related, such as keeping physical distance and washing hands frequently (Alwan et al, 2020;Chu et al, 2020;Ioannidis, 2020;Jones et al, 2020;Rundle et al, 2020). Third, while previously studied behaviours have direct personal benefits, this is not the case for COVID-19 recommendations.…”

Aerosol Release by Healthy People during Speaking: Possible Contribution to the Transmission of SARS-CoV-2

“…Their elements are occupancy of rooms, meeting time, activity (breathing, speaking, and shouting), and wearing of face coverings. The authors clearly demonstrated that the risk of infection increases with occupancy and presence of SARS-CoV-2 in most situations reviewed [29].…”