Covid-19: Does wearing masks offer protection against viruses?

摘要

There seems little doubt that the dispersion of Covid-19 droplets is reduced when people wear masks or face coverings. However, what is controversial is whether masks, of which there are many types, will protect wearers against the inhalation of the virus. Experiments performed at the Animal Virus Research Institute, Pirbright, Surrey (now The Pirbright Institute), many years ago are relevant to the debate.