If 80% of people wore masks when leaving their homes, COVID-19 transmission rates would be better contained, a UC Berkeley researcher and his team found in a study released April 21.
Dekai Wu, a researcher at UC Berkeley’s International Computer Science Institute and a professor at the Hong Kong University of Science and Technology, first came up with the idea for the study in February, when he noticed the difference in COVID-19 response between California and Hong Kong, especially in mask use. His research group — an interdisciplinary team of global researchers — found there is almost a 100% correlation between countries that have implemented early universal masking policies and those that have suppressed the spread of the coronavirus.
“Ninety-nine percent of people are walking around wearing masks in Hong Kong,” said De Kai, as he is more commonly known. “In Hong Kong, we’ve actually never had to have shelter in place because we’ve done the other things right.”
The study uses two types of models to predict the impact of masks on infection rates throughout the population. The first is called the susceptible-exposed-infected-recovered, or SEIR, model, which is a traditional epidemiological method that sorts theoretical individuals into one of the four categories according to whom they come in contact with based on mathematical equations. When susceptible people interact with infected actors, they become exposed and eventually infectious, which allows them to spread the disease to other people until they recover.
The problem with this, according to De Kai, is mathematical equations make it hard to account for strategies such as social distancing. He developed the study’s second method — agent-based modeling, or ABM — to account for these variables more accurately.
Both methods showed that masks are highly effective if universal mask policies are implemented by day 50 of a region’s outbreak and if 80% of the population wears a mask, according to the study.
“Universal masking is cheap and simple,” said University of Cambridge lecturer Alexey Morgunov in an email. “People need to understand that wearing face masks in public is important to save lives and to get as much of our normal lives back as possible.”
Included in the study is a link to an online simulator where people can watch the results of the experiment change as they toggle with the percentage of the population that wears masks and how effective the masks are, among other variables.
De Kai said it was important for him to include the simulator because he wanted people to be able to visualize the research, as the effects of masking policies are logarithmic and can be hard to understand.
“I felt that it was very important for people to understand for themselves the counterintuitive behavior of masking,” De Kai said. “To nonspecialists, the exponential behavior of epidemics is not what you’d expect.”
The researchers have begun to spread the word about the importance of universal masking, including by signing a letter in favor of a universal masking policy that was sent to the governors of all 50 U.S. states. Guy-Philippe Goldstein, a researcher from Ecole de Guerre Economique in France, said he has been appearing on the French equivalent of CNN to spread the word.
Both Goldstein and De Kai added, however, that universal masking policies alone will not be sufficient to stop the transmission of COVID-19. They added that people should continue to socially distance, increase the capacity of testing for the disease and contact trace the infected population to determine whom they have been in contact with.
“It’s so obvious that it’s, economically speaking, a no-brainer. Masks cost nothing, and it may bring about a good measure of protection,” Goldstein said. “There is no reason why we should not be all masking.”