Dr David Carrington, of St George's, University of London, told BBC News " routine surgical masks for the public are not an effective protection against viruses or bacteria carried in the air", which was how "most viruses" were transmitted, because they were too loose, had no air filter and left the eyes exposed.
But they could help lower the risk of contracting a virus through the " splash" from a sneeze or a cough and provide some protection against hand-to-mouth transmissions. https://www.bbc.com/news/health-51205344
主要是预防用手碰脸，很多人会习惯性地用手碰嘴巴。
同时可以预防其他人喷嚏和咳嗽时的唾液喷溅
不要指望口罩能高效预防病毒传染，但带总比不带好
Dr David Carrington, of St George's, University of London, told BBC News "
routine surgical masks for the public are not an effective protection
against viruses or bacteria carried in the air", which was how "most viruses" were transmitted, because they were too loose, had no air filter and left the eyes exposed.
But they could help lower the risk of contracting a virus through the "
splash" from a sneeze or a cough and provide some protection against hand-to-mouth transmissions.
https://www.bbc.com/news/health-51205344