Prevention of viral infection, mask against contamination linked to viruses. The surgical mask is a means of prevention against the risks of virus contamination. Viruses are contagious. They need a host cell to replicate. Some viruses can be transmitted from human to human through droplets of water that are sputtered during sneezing and speaking. The mask helps block the spread of these droplets by people with viral disease with this type of transmission through the respiratory tract. Strasbourg, Bas-Rhin, France.