How long the coronavirus remains in the air: scientists answer
'30.04.2020'
Source: Газета.ру
Coronavirus spreads even when breathing and talking, Chinese scientists found. It is not yet known how viable the viral particles remaining in the microdrops are in the air, but researchers recommend avoiding crowded places and poorly ventilated rooms, writes "Gazeta.ru".
Coronavirus is able to spread through micro-droplets of secretions resulting from talking and breathing, warn Chinese scientists from Hong Kong University of Science and Technology and other research centers. They reported this in an article in the journal Nature.
Previously, scientists have already shown such a possibility in experiments, but now it was possible to detect microdroplets containing SARS-CoV-2 coronavirus RNA in two hospitals in Wuhan where patients with COVID-19 were treated. Samples were collected in February-March 2020. Researchers also took air samples from supermarkets and apartment buildings.
Wherever patients with coronavirus were present, microdrops of secretions with a diameter of less than a few thousandths of a millimeter containing virus particles were found in the air.
Their lowest concentration was in well-ventilated hospital wards. The largest - in toilets that were poorly ventilated.
In residential buildings and supermarkets, the virus was not present, although it was found in crowded places near one of the hospitals. But the concentration was low - it would take about 15 minutes for at least one viral particle to enter the human body.
Traces of the virus were also found in the air in places where hospital staff took off their protective suits - apparently, the virus particles got there in the process of changing clothes. After more stringent cleaning procedures were introduced in hospitals, the number of virions in the air decreased significantly.
Data from Wuhan echoes the data from the medical center at the University of Nebraska in the United States. There, researchers also managed to detect coronavirus RNA in the air and on surfaces - for example, on window sills and under beds in hospitals. The work has not yet been published, but the authors believe that it is all about microdrops carried by air currents.
Neither Chinese nor American scientists can yet say how viable the virus is, carried in this way.
They are currently busy trying to figure it out. However, the microdrops released during breathing extend at least to the distance of the outstretched arm and are able to remain in the air for more than two hours, which creates the potential for infection.
“Microdroplets will be in the air for at least two hours,” said Professor Lindsay Marr of Virginia Polytechnic. “This implies that the virus has great potential for transmission through the air.”
On the subject: How long does a person with a coronavirus remain contagious: CDC explanation
“We have made great progress over the past couple of weeks,” said Joshua Santarpia, a professor of microbiology at the University of Nebraska. “I really hope that we can say something more specific next week or so.”
Until now, it was believed that the virus spreads through larger droplets or through contact with infected surfaces, the researchers explain. They believe that so far WHO has underestimated the potential of its transmission simply by breathing.
While there is no accurate data on the viability of the virus in the air, the researchers recommend avoiding small enclosed spaces and crowds, as well as remember to ventilate the rooms.
It is also unknown whether people who visited the sites where the virus was detected wore masks.
It remains to be seen how well they hold microdrops spread by an infected person.
Previously, physicists sounded the alarm about the spread of coronavirus through the air. The Belgian scientist Bert Blocken calculated using aerodynamic modeling - depending on the way a person moves, the safe distance between people can be up to 20 m.
On the subject: Fresh data: scientists specified how long coronavirus lives on different surfaces
“When someone exhales, coughs or sneezes while walking, running or cycling, most of the droplets are behind the person,” Blocken explained. “And the one who goes, runs or rides after him finds himself in this stream of air and moves through a cloud of drops.”
Moving side by side with someone is safer than going after him, the scientist noted. Being behind someone who goes fast enough, you should keep at least 4,5 m from him.
If a person is running, you should retreat 10 meters, and the cyclist should be 20 meters away.
Another way to avoid getting into the stream is to move a couple of meters to the side. When overtaking, Blocken recommends making sure that the person who is behind you does not fall into your “affected area”.
