Winter colds

[Jarnold]

Why do we get more colds and flu in winter? Why not in summer, too?

[tonyb]

There are a number of reasons reason people are more likely to come down with a cold or flu at the coldest time of the year. For a start, the rhinovirus (the bug responsible for as many as 40% of the colds we catch) grows better at temperatures lower than body temperature. The lining of the nose in winter is the perfect place. Next, we spend a lot more time indoors in winter, which means more people spending time in badly ventilated rooms and buildings, with nothing better to do than pass on germs to each other. Also, the ultraviolet rays in sunshine kill viruses and there's a lot less sunlight around when the days are short. And just to make sure the bugs get the best selection of people possible - all the nurseries, schools and universities go back in autumn. Children, who have only been in contact with a few of the 200 cold viruses available, are ripe for infection with some new ones.

[incitatus]

There was a suggestion recently that the new flu bugs which start in the autumn may be originally spread by migrating birds. Many flus originate in birds, then go through several; mutations before latching on to humans and forcing them to drink whiskey as a cure.