KEY POINTS
  • The study was released Sunday by the department of microbiology at The University of Hong Kong.
  • Local media reports stated it will be published in the Clinical Infectious Diseases medical journal, suggesting it is yet to be peer reviewed.

As the debate over the effectiveness of wearing masks during a pandemic continues, a new study gives weight to arguments by medical professionals and government leaders that wearing a mask does indeed reduce virus transmission — and dramatically so. 

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 study was released by the department of microbiology at The University of Hong Kong, and local media state it will be published in the Clinical Infectious Diseases medical journal, suggesting it is yet to be peer reviewed. The sample size was also reportedly in the double digits.

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.  

"In our hamster experiment, it shows very clearly that if infected hamsters or humans — especially asymptomatic or symptomatic ones — put on masks, they actually protect other people. That's the strongest result we showed here," Yuen said. 

"Transmission can be reduced by 50 (percentage points) when surgical masks are used, especially when masks are worn by infected individuals," he said. 

Hamsters have very similar enzyme receptors to humans, which is why they were chosen as the test animals for Yuen's experiment. 

"Up to this stage, we do not have a safe and effective vaccine. What remains practical is still either social-distancing measures or wearing masks," Yuen added.