Not even the air of empty spaces is coronavirus free (Two meters is not a safe distance)

Crema, Edilson

A key safety measure encouraged by health authorities to avoid the SARS-CoV-2 spreading is the distance of one to two meters between people. This recommended two-meters distance is mainly based on short-distance contagion, when infected drops are expelled during a speech, coughing, or sneezing and directly hit another person. The dangerous form of airway contamination caused by droplets that remain suspended in the air for several hours has been almost ignored. However, the theoretical calculations performed in this work, recent experiments, and the accumulated knowledge in this and other epidemics indicate that, because of the airborne transmission, there is no safe distance to the coronavirus, either indoors or in open places. Recent investigations have confirmed not only the presence of the coronavirus in droplets suspended in the air but that these viruses remain active for several hours. Furthermore, significant indirect evidence of this means of transmission is the great difference in contagion between Brazilian regions in the current outbreak. While the Amazonian states have a contamination rate greater than 20%, in the southern states of the country this rate is less than 1%, despite high temperatures in the Northern region. Notwithstanding the social and economic differences between these regions, it seems that the extremely high humidity of the forest air prolongs the survival of the viruses in the drops in the external environment. Our theoretical calculations explain empirical observations from recent epidemiological studies and strengthen the need to use, not only a mask but also protective glasses throughout the population in the same way that they are mandatory for health professionals. Besides, our calculations show how air conditioning and heating systems can increase contagion. Finally, we suggest measures that could reduce the spread of the pandemic.