I saw some photos in the paper of quite a few inventive solutions to the shortage of surgical masks in China. Some people had made one from a plastic bottle cut into shape. Even the leaves of a large cabbage(!) and one young woman had attached the peel of half an orange to her face. Bras are apparently useful. But it seems that washing the hands thoroughly after being out is an excellent idea, also avoiding touching handrails/stair rails or doorknobs, then one's face.