One day you’re feeling fine, the next, your nose is running, you’re sneezing and your throat feels like you’ve swallowed broken glass. Welcome to the annual cold season. Most of us will get between one and three colds each year, usually in autumn and winter, caused by one of more than 200 different cold viruses. And there is little you can do about it — a cure for the common cold remains one of the Holy Grails of medicine — but better understanding of how these viruses spread could be the key. What we do know for sure is that...