Narrow spaces, such as public transport and public buildings, should be avoided. Good ventilation that takes in clean air from the outside, are further measures and recommendations the researchers believe should be taken.

"Washing hands and social distancing is appropriate, but we believe that it is not enough to protect from microdrops with viruses that infect people are exhaling," writes over 200 researchers in an open letter to WHO.

Smaller drops

The researchers believe that the infection risk has been underestimated. If the corona virus is airborne, it means that the particles can reach more than a few meters, and even stay in the air longer than classic droplet infection.

The droplets and particles that come out of a person who coughs or sneezes are both larger and heavier than those that are exhaled, according to the researchers.

Over 200 researchers

The report is written by 239 researchers from 32 different countries.

The World Health Organization (WHO), as well as the Public Health Agency, considers so far that covid-19 is primarily spread through drip infection.

- If an airborne infection were to drive this, we would have seen a completely different scenario. It is an obvious drip infection, but in some situations you can get something that is more reminiscent of airborne infection, says Director General of the Public Health Authority Johan Carlson at Tuesday's press conference.

WHO reviews

WHO is now reviewing the researchers' report, Reuters news agency writes. Should the new findings be sufficiently convincing, it could mean that the WHO is updating the current recommendations.

The researchers also write that airborne contamination is the only reasonable explanation for the so-called super-spreaders.