Coronavirus: How does the virus spread in indoor air? – Health


How exactly the coronavirus SARS-CoV-2 is spread – whether mainly via a droplet infection or rather via aerosols in the air we breathe – has not yet been conclusively clarified, according to a current report from the Technical University (TU) Berlin.

The novel coronavirus is probably mainly transmitted via droplet infection, most likely via the nose, as a recent study showed.

In addition, there are indications that SARS-CoV-2 can be transmitted via aerosols, explains the Federal Centre for Health Education (BZgA) on its portal “Infektionsschutz.


Transmission via faeces also seems possible.

However, a final evaluation is still difficult at this stage.

It is known that the coronavirus SARS-CoV-2 is transmissible from person to person.

According to current knowledge, the main transmission route appears to be droplet infection.

However, many aspects of the risk of infection are still unclear.

Researchers are therefore looking into the various transmission paths.

Coronavirus: Scientific studies on transmission paths

When a Corona infected person coughs, talks or sneezes, a jet of droplets and aerosols of different sizes is produced, which penetrates into the room air and spreads out there.

All these different sized droplets and aerosols can potentially contain viruses.

How these particles behave, if and when they sink to the ground, how far they spread, remain in the air or where they sediment, is a current research topic of Prof.


Martin Kriegel, Director of the Hermann Rietschel Institute at the TU Berlin.

“In various projects, we are investigating the residence time of pathogens in the air under the most diverse conditions,” explains Martin Kriegel.

No final clarification yet

In connection with the corona pandemic, scientists are investigating the extent to which the spread of the virus depends on the composition and size distribution of particles within the exhaled air (aerosol).

An aerosol (droplet nuclei floating in the air smaller than 5 micrometers; for comparison: a human hair is about 100 micrometers thick) consists of tiny liquid or solid particles (these can be viruses, for example, individually or in combination with saliva or soot, fine dust, etc.).

) in a gas, usually air.

As explained in the communication, when a droplet infection occurs, the virus particles in a droplet of saliva get directly onto the mucous membranes of another person.

In the case of airborne transmission, the pathogens – bound in minute liquid particles – enter the respiratory tract.

“For the corona virus, it appears that both droplet infections and airborne transmission, i.e. via aerosols, are relevant,” says Martin Kriegel.

According to the information provided, the spread in the space of the mixture of particles, saliva and air, which is produced when speaking, coughing and sneezing, occurs in two steps.

First, the coughing/speaking/sneezing generates a jet that penetrates the air in the room and increasingly mixes with it.

According to the experts, the course of the incoming jet depends on various boundary conditions such as speed, turbulence, the temperature difference between the jet and the ambient air and the difference in humidity.

“Larger particles sink to the ground faster.

Smaller particles follow the air stream and can remain in the air for a long time,” says Martin Kriegel.

The size of the carrier aerosols is decisive for the behaviour of viruses in the air, but also the room climate, the air exchange rate and the way in which the air is ventilated.

WashingtonNewsday Health


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