American physicist Bourguiba Lydia (Lydia Bourouiba) have shown that the drops spread by sneezing in a cloud of 7-8 meters from the source and are in the air much longer than previously thought. Existing models of the spread droplets of the suspension, which is obtained by sneezing, are based on outdated data of the 1930-ies. About it it is reported in Journal of American Medical Association.
In the first half of the XX century it became clear that the causative agents of some infectious diseases are transmitted from person to person from airborne suspension when sneezing or coughing. One of the main researchers of this issue William wells suggestedthat the drop in such suspensions are divided into two groups: large and small.
Large, according to wells, quickly deposited in a small radius from someone who sneezed or coughed, and little remain in the air longer, but then the water in them evaporates and pathogens remain in the dried form. These data, as he wrote to wells, largely theoretical, but they are still used in the recommendations to prevent the spread of some infectious diseases.
Bourguiba Lydia (Lydia Bourouiba) from the Massachusetts Institute of technology Sheila to record rapidne camera (frequency of 2,000 frames per second) the process of sneezing, estimate the settling velocity of droplets of different sizes and measuring how far they fly. It turned out that the cloud droplets covers 7-8 meters. Settling, they contaminate surfaces with pathogens. It is important not only drop diameter: depending on the humidity of their suspension may be delayed from several seconds to several minutes.
The author suggests that these data may be important to deal with the current pandemic COVID-19. They do not contradict that found employees of Singapore hospitals: where patients infected by the coronavirus, even when the air of the room didn’t find it: probably SARS-CoV-2 with a cloud of particles thrown out by patients while coughing or sneezing, got into the ventilation and spread through her. Disinfection of surfaces helped to get rid of the virus.
Yet to limit the spread of the disease Center for control and prevention of morbidity of the USA advises medical professionals to keep a distance approximately two meters from the cases, the world health organization — at a distance of meters. But perhaps that distance should increase.