Could Covid-19 spread by microparticles from our own breathing and conversations? A group of scientists believes that it is and they are about to demonstrate it with a simple collection exercise in a hospital room.
A team from the University of Nebraska first managed to replicate SARS-CoV-2 particles collected from the air in patients rooms with Covid-19. This reinforces the hypothesis that the virus is transmissible not only in the large droplets emitted by coughs and sneezes, but also by the microscopic droplets that we release when we breathe and speak, and that they are so light that they remain in suspension for a long time, in the absence of ventilation.
Anyway, the results of this scientific study are preliminary and have not yet been examined by the reading committee of a specialized magazine, which will have to confirm that the method used by the scientists is valid. This demonstration was published Monday on the site medrxiv.org, where the scientific community can freely comment. But the same team had previously published a study in March that showed the virus remained in the air in hospital patient rooms, and this article will soon be published in a scientific journal, according to the lead author.
«It is not easy,» said Joshua Santarpia, a professor at the University of Nebraska Medical Center, about the method of collecting viral particles in the air, using a device the size of a cell phone. «The concentrations are low, there is generally little chance of recovering usable samples,» he added.
The researchers took air samples in the rooms of five patients about 30 cm above their feet. The patients spoke, some coughed. Scientists have managed to collect microdroplets less than five microns in diameter that contain viruses, and even less than one micron.
They then isolated the virus and placed it in a special medium for it to replicate. Only three of the 18 samples from one-micron drops were able to replicate with certainty. But Joshua Santarpia is sure: «it replicates in the cell culture and, therefore, it is infectious.»
The airborne route of transmission was considered unlikely at the start of the pandemic by health authorities in several countries and the World Health Organization, who believe that direct contamination (by spray and drops directly projected on the face) remains the main contagion path. But the WHO, under pressure from scientists, admitted on July 7 that evidence of airborne transmission was emerging.
«The debate has become more political than scientific. I think most infectious disease scientists agree that the airway is a component of transmission, although we are still debating its importance», says Joshua Santarpia.
Professor Linsey Marr, a specialist in airborne virus transmission, commented on Twitter that the study presented «strong evidence» and added: «There are infectious viruses in the air.» It remains to be seen how much to breathe to be infected. ” A «detail» of utmost importance.
A study that corroborates the opinion of many international experts. According to these 239 researchers and scientists based on experiments in 32 countries, coronavirus is also transmitted «through much smaller expired drops» and this air «can infect people when inhaled.»
This could happen by simply speaking or exhaling air while breathing, especially if people are not protected by a mask, and not just coughing or spitting. «We have known since 1946 that coughing and talking create aerosols,» said Linsey Marr, a virus transmission specialist at Virginia Tech, in the New York Times in early July.
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