Scientists studying bioaerosols – small drops of dry saliva that can carry viral particles and stay in the air for several hours – came aboard to study the effectiveness of facial masks and help answer practical questions such as choosing the most appropriate fabric and design. Not surprisingly, soon after cities like Hong Kong, which were heavily affected by the first SARS virus in 2003, the first cases of VIDOC-19 were reported, and in countries like Taiwan, almost everyone started wearing face masks. Since then, masks have played an important role worldwide in the fight against respiratory pandemics over the years,” said Jeremy Howard, a data researcher and resident researcher at the University of San Francisco. After masks helped stop one of the worst outbreaks of infectious diseases in history, Wu would be surprised to discover, Linteris said, that some people still don’t believe in them. A study conducted by the Associated Press-NORC Public Affairs Research Center in July found that 86 percent of Americans reported wearing a face mask when they left home, compared to 73 percent in May. Another study published in Nature Medicine in May found that surgical masks effectively block viral particles from seasonal crown and flu viruses and concluded that masks can prevent transmission of these infections. But since the particles grow only slightly, around 2 µm, “the ones we consider most important block transmission of almost all the different substances we test, and the types of masks block at least half of them,” he says. He’s tried different facial mask fabrics and different face mask configurations, as well as different droplet sizes, from small floating sprays to sputum fat droplets that fall to the ground quickly after coughing or sneezing. Marr says that if you need a good face mask, the type of fabric is not as important as diapers. Mongolia, a country with 3 million inhabitants on the border between China and Russia, also adopted a wide use of masks at the beginning of the pandemic, with only 300 cases recorded and no deaths. Andrews, Scotland, who studied the social significance of face masks, believes that the reasons why a mask is not worn are more complicated than political reasons of parties. And once the particles are reduced to about 5 microns, most tissue masks block about 80% of them,” he says. First of all, only n95 masks, dome-shaped respirators and a block of smaller aerosols, which explains their importance for healthcare workers who need a high level of protection. National Academy of Sciences, “Quick Expert Consultation on the Efficacy of Tissue Masks for KOVID 19 Pandemic”, April 8, 2020. Howard came across the story of Wu when he gathered a study on facial masks earlier this year. Linteris says he recently observed a group of young people changing the same mask on a glacier.