Why you get a cold in cold weather

Dear Matthew (Doc) Alice: My Frau is a recent transplant from Germany. She believes that the frequent temperature swings we experience in San Diego’s autumn (often compelling her to add or remove extra clothing several times a day) directly expose her to a much higher risk of seasonal illness (colds, flu) than would be the case in Germany, where, come autumn, it turns cold, stays cold, and you never go out without the protection of warm clothing. I argue that we humans, unlike reptiles, are able to regulate our body temperature and, barring extreme exposure, are put at no physical risk due to changes in our surrounding temperature. I believe that more people get sick in cooler weather because they congregate more indoors thus increasing their risk of being exposed to harmful germs. — Joe and Perpetua Ryan, Pacific Beach

I’m glad to take this opportunity to clear up the universal misconception that you get a “cold” from being cold. Or from being too hot and then too cold. Or from sitting in a draft. You get a cold or the flu by coming in contact with germs, not weather. In general, colds and flu are more common in the winter because we spend more time indoors, germs can be more easily spread through sneezes, coughs, or from coming in contact with germ-laden body fluids in other ways. But medical researchers have noted seasonal patterns for many illnesses — measles, mumps, and chicken pox outbreaks are more common in the spring and summer, for example. As a result, investigators have mapped cyclical variations in white blood cell counts and other components of our bodies’ immune response to invading pathogens, which might also account for illnesses blamed on the weather.