The WHO announced on 5 June that “governments should encourage the general public to wear masks where there is widespread transmission and physical distancing is difficult, such as on public transport, in shops or in other confined or crowded environments”. People over 60, as well as those in high-risk groups, should wear medical grade masks and all others should wear a three-layer fabric mask, WHO advises. Masks are not a standalone measure and are only effective when used in combination with frequent hand cleaning with soap and water or an alcohol-based hand sanitiser product; avoiding touching eyes, nose and mouth at all times; and social distancing measures.

Even then, masks have to be used correctly. The covering should extend over the mouth and nose, with no gaps between the face and cloth. The mask should not be touched while being worn, and if it is, hands should be immediately cleaned thoroughly. If the mask becomes damp, it should be replaced by removing it from behind (without touching the front), discarding into a closed container such as a plastic bag, cleaning hands and then putting on a new one. Used fabric face masks can be washed with other laundry using normal detergent, and while the best textiles to use are tightly woven cottons or twill, natural silk, or quilted cotton, anything with a close weave is suitable. For face masks that have a filter pocket, a sheet of kitchen roll can be used as a filter.

There are downsides to using face coverings, such as giving a false sense of security, with individuals wearing them tending to overlook other, often more effective, measures as a consequence. They can also be contaminated by the individual wearing them, or by other people coughing and sneezing and, if not replaced or laundered, can actually act as a reservoir for infection. There can be other problems too, from discomfort and breakdown of facial skin from frequent or constant wearing, to difficulties with breathing or communication.