This article originally appeared on VICE US.
Researchers in China who examined how the coronavirus spread through two Wuhan hospitals at the height of the outbreak there have found evidence that it can be transmitted through the air.
The research was published this week in Nature and says that while the transmission of COVID-19 through human respiratory droplets and direct contact is clear, “the potential for aerosol transmission is poorly understood.”
In order to better understand how the virus spreads, the researchers captured samples “in different areas of two Wuhan hospitals during the COVID-19 outbreak in February and March 2020.”
Then they identified the genetic markers of the virus in airborne droplets, many with diameters smaller than one ten-thousandth of an inch — which could potentially stay airborne for several hours.
“Those are going to stay in the air floating around for at least two hours,” Linsey Marr, a professor of civil and environmental engineering at Virginia Tech who was not involved with the Nature paper, told the New York Times. “It strongly suggests that there is potential for airborne transmission.”
However, the scientists warned that the presence of COVID-19 RNA — the genetic blueprint for the virus — does not mean that these airborne droplets are infectious.
To date, most efforts to stop the spread of the virus, such as social distancing, have been based on the belief the virus is not transmitted through the air. If it was found conclusively that the virus was transmissible through the air, it would significantly strengthen the case for mandatory mask-wearing to stop the spread of COVID-19.
The researchers, who come from a variety of Chinese universities and laboratories, found that the concentration of the coronavirus in aerosols in isolation wards and patient rooms was very low due to good ventilation, but found that it was much higher in confined spaces, like patients’ toilet areas.
The report also found elevated levels in the areas where doctors and nurses took off their personal protective equipment (PPE), suggesting that droplets that had landed on the surface of the gear could be knocked back into the air.
Researchers suggest that factors such as room ventilation, open space, sanitization of protective apparel, and proper use and disinfection of toilet areas can reduce the concentration of COVID-19 aerosol concentration.
The study is just the latest to suggest coronavirus can be transmitted through the air.
A recent study by the University of Nebraska Medical Center found coronavirus RNA in the air as well as on surfaces in rooms — though the research is still being peer-reviewed before being published in a medical journal.
The same scientists are now trying to grow the virus in laboratory conditions from the airborne samples they captured to determine whether or not it is infectious.
The World Health Organization has continued to downplay the threat of aerosol transmission, saying the virus primarily spreads through larger droplets that don’t stay airborne for a long time, or through contaminated surfaces.
Cover: Medical staff put on isolation gears in a hospital designated for COVID-19 patients in Wuhan in central China's Hubei province Monday, Feb. 24, 2020. Doctors and nurses of other disciplines in the hospital were all assigned to respiratory patients upon the official announcement of the outbreak, and 51 of them contracted SARS-COV-2 during that time due to lack of protection. Their first reinforcement of 138 medical personnel came to rescue on Jan. 26. (FeatureChina via AP Images)