Is “stay at home” the correct social distancing measure to fight the covid-19 pandemic ?

While social distancing has been shown to be an effective measure to break transmission chains in previous pandemics, as the 1919 flu pandemic and the 2014 Ebola outbreak (Caley et al., 2008; Tuncer et al., 2018), its interpretation in western societies has been focused instead to the “stay at home” message, in the sense that any open-air activity is stigmatized as dangerous and irresponsible, leading to widespread parks and beaches closure and a modern-day witch hunt toward anyone running, swimming or just walking outdoor.

Covid-19 is however a respiratory disease, not a toxic cloud. Scientific evidence points that while fomite transmission (trough infected objects) seems plausible, the virus primarily spreads between people via respiratory droplets from coughing or sneezing and the resulting aerosol (van Doremalen et al., 2020; Liu et al., 2020b) as for the other known coronaviruses (Kim et al., 2016).

However the virus concentration becomes negligible in outdoor environments, and according to the Wells–Riley equation, the probability of infection through infectious droplet nuclei is inversely correlated to the ventilation rate (Atkinson J, 2009). Hence the probabilities of transmissions in outdoor environments, even in proximity, is much reduced (according to…