Spreading coronavirus via aerosols sometimes seems possible: we now know this | NOW

Tiny droplets that float in the air for a long time, so-called aerosols, were a major topic of debate this spring and summer. Are they contributing to the spread of the coronavirus and what have we learned about this since May this year? This is the state of affairs.

Both it RIVM, the US health authority CDC as a health organization WHO argue that under specific circumstances, the coronavirus may be able to spread via aerosols. This could occur, for example, in busy, poorly ventilated areas.

What are aerosols again?

Aerosols are very small droplets that you release when you talk, breathe, cough and sneeze. In addition to aerosols, you also emit larger droplets. The corona virus can be contained in both aerosols and larger droplets. Due to its volume, one large drop can contain more virus than one aerosol.

Aerosols do get a lot of attention in the corona discussion because they can stay in the air much longer and travel longer distances than larger droplets due to their limited weight. They can therefore also travel more than 1.5 meters. If aerosols do indeed spread the coronavirus, this will have consequences for which measures you should take against the virus. For example, we know that ventilation helps against dispersion via aerosols.

However, according to the WHO, aerosols are not expected to play a major role in the spread of the coronavirus. They argue that the virus mainly spreads through direct contact, such as kissing, indirect contact (for example, through doorknobs or shopping carts) and close contact at close range, such as having a long conversation without staying 1.5 meters away. The CDC and RIVM also do not expect aerosols to be the main spread of the corona virus. All authorities say that more research is needed.

Virus detected in hospital air room

This research is currently taking place in several places around the world. That’s how NU.nl was in at the time May wrote about what we knew about aerosol diffusion, it has not yet been shown that there can be airborne coronavirus at all relatively far away from an infectious person, which is still intact enough to infect humans.

A group American researchers has already demonstrated this, thanks to a device that is better than most sample devices capable of catching viruses without damaging them. They found in air samples taken at a considerable distance (between 2 and 4.8 meters) from an admitted COVID-19 patient coronavirus that was sufficiently intact to be contagious.

Sander Autumn, molecular virologist at Erasmus MC, explains that we do not yet know how much contagious coronavirus you have to inhale before you become infected yourself. We do not know how long you can be in a room with a COVID-19 patient without becoming infected yourself.

Big differences between infected people

This most likely also differs greatly per infected person. A group of researchers, including Marion Koopmans of Erasmus MC, found out that a small proportion of people infected with the corona virus emit so much virus in large and small droplets that it is in any case likely that they can infect other people via aerosols . How often this happens, and under what circumstances, we do not know yet.

The majority of people infected with the corona virus are unlikely to spread via aerosols, because they emit too little virus for this.

Research into dissemination remains difficult

The situations in which the coronavirus spreads via aerosols are difficult to investigate with experiments because it is ethically complicated to intentionally infect people with the corona virus. Investigation after a known contamination is also complex, because it can often not be ruled out afterwards that people have become infected via a route other than aerosols.

Autumn is conducting research with ferrets to find out how coronavirus infections could develop. In May, he explained that ferrets placed 10 inches apart can infect each other without direct contact. It was impossible to say whether the contamination then proceeds via larger droplets or through aerosols. There is now one pre-publication posted online showing that ferrets can infect each other from 1 meter away.

It is still not known what infects ferrets. Both very small and larger droplets were able to bridge the distance of 1 meter. It is also theoretically possible that viruses on, for example, dust particles or hair that blown over, played a role in the spread. In addition, Autumn emphasizes that results on how easily the virus spreads in ferrets cannot be directly translated to humans. Ferrets seem to be more sensitive to coronavirus infections than humans.

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