In most cases infection by Corona virus is caused by microdroplets containing fully active virus particles, set free by coughing fits or sneezing or contact with hands or matter contaminated by microdroplets containing fully active Corona viruses. Mouthwash with liquid agents containing antiviral components might be a mean to avoid infection. Agents of this kind, though primarily used against bacteria, in some cases contain also antiviral components. This
property might be supported by addition of tannin to the liquid agent. Tannins are known to be also active against „enveloped“ viruses. Tannin causes denaturation of proteins. A trial might be appropriate in order to test whether tannin also denatures the proteins on the surface of the Corona virus (e.g. the „spikes“ needed for contact with the surface of human cells). Tannins as agents in combination with other components are used in medicine as agents for a wide number of treatments.