A few days ago a very interesting article was published in the prestigious PNAS journal by an American team from the University of Philadelphia (Stadnytskyi et al, May 2020) that could shed light on a possible cause of infection of novel coronavirus in closed environments. Scientists have observed that talking can generate thousands of droplets that remain in the air for up to 14 minutes. But let's understand better.
Coronavirus, how infection can occur
As we know, contagion can occur by direct contact with infected saliva droplets emitted by sick people who sneeze or cough. But there are also other ways of infection. Infected droplets, in fact, can settle on surfaces and if a person comes into contact with these surfaces, for example by touching them, and then he or she brings the hands to the face, infection is possible. Not only that, as the research we are talking about today has observed, the droplets emitted when speaking can remain in the air for up to 14 minutes and from there they can be inhaled by other people.
Coronavirus, we explain the experiment
Scientists asked volunteers to speak inside a cardboard box by repeating a sentence, stay healthy. Thanks to the use of green lasers, the researchers studied the emission of saliva droplets, assessing their life span and also their size. This last aspect is important because, once emitted, the droplets become smaller due to evaporation and this can determine the speed of the particles falling to the ground, which slows down as the size decreases, and the probability of containing the virus. What the researchers have seen is that in one minute of talk, an infected person can produce up to 1000 infected droplets that remain in the air from 8 to 14 minutes.
Consequences of the experiment, its limits and the problem of closed environments - The experiment is very important. Certainly it is limited since it analyzes the situation in an environment too far from the real one, without evaluating the air flows. In addition, it does not consider how much virus the droplets have to contain to be truly infected. However, the results should be taken into consideration, especially to assess the risk in closed environments such as restaurants or shops and the action of asymptomatic people. For this reason, it is important, especially in closed environments, in addition to respecting social distancing, to wear masks and to air the rooms often.