Experiments by a team in Hong Kong found that the coronavirus’ transmission rate via respiratory droplets or airborne particles dropped by as much as 75% when surgical masks were used. “The findings implied to the world and the public is that the effectiveness of mask-wearing against the coronavirus pandemic is huge,” Dr. Yuen Kwok-yung, a leading microbiologist from Hong Kong University who helped discover the SARS virus in 2003, said Sunday.
The team’s conclusion comes after months of conflicting information from world health bodies concerning masks. The World Health Organization has questioned their effectiveness outside of medical settings, while governments including those in the U.S. and U.K. initially urged citizens to leave them for health worker use, only to later make a U-turn and encourage widespread mask-wearing.
The study, which the Hong Kong team calls the first of its kind, used hamsters in two cages; one group of hamsters infected with Covid-19 and the other healthy. The researchers created three different scenarios: mask barriers placed just on cages with the infected subjects, masks covering the healthy subjects, and one with no mask barriers at all, with a fan between the cages allowing particles to be transmitted between them.
With no mask barriers at all, two-thirds of the healthy hamsters — 66.7% — were infected with the virus within a week, the researchers found.
When the mask was placed over the infected cage, however, that infection rate dropped to 16.7%. The infection rate went up to 33% when the mask barrier was only used to cover the healthy hamsters’ cage.
The hamsters who were still infected despite having the mask barrier also had less of the virus in their bodies compared to those infected without the masks, the researchers found.