Yes, everyone seems to be getting sick. This year has been especially bad with the high prevalence of H1N1 influenza. In fact, in the laboratory I teach, we had to lighten the attendance policy to allow repeatedly sick students to pass the course.
With all of these things going on, it might get you thinking…why now? Why do we always get sick more in the winter? Well to answer that question let’s look at the conventional wisdom. If you ask just about anybody off the street, they’ll tell you that the cold somehow weakens your body (maybe your immune system) and makes you more susceptible to disease. How do they know this? Well their mothers told them, of course!
Everyone has heard the phrase “Bundle up or you’ll catch a cold!” But how accurate is that statement really? Our body depends on an idea known as “homeostasis,” which describes the ability of a system to maintain itself. While the outer temperature of your body varies widely based on environmental conditions, the core temperature remains constant. Most people have a core body temperature of 98.6°F (37.0°C). If you think about it, the only time that your temperature changes is when you have a fever. Fevers only happen when the body specifically raises its temperature to fight off infections.
So how does this affect our initial question? Well, if your internal temperature remains fairly constant in any weather, why does sickness increase in the winter? Almost every microbiology course I’ve taken has posed this question, because it’s a good one to make you think scientifically instead of anecdotally (relying on “conventional wisdom”).
As it turns out, one of the other effects of winter is that people tend to stay indoors more often. When the population stays indoors (in a closed air system) and in the presence of others for an extended period, the rate of infection increases. This is because at any given time, there are a few individuals infected with one of the many reoccurring (endemic) diseases. If those people had only limited contact with others, they might spread their colds or they might not. When they stay inside with everyone else, though, they successfully infect many more people.
While this answer may surprise some of you, I think the more impressive take-away is the regulatory ability of the human nude body. Despite cold winds or a scorching sun, we maintain that core body temperature like it’s our job. In some respects, it IS our body’s job. All living things must find ways to maintain internal conditions such as temperature, pH, and sources of energy. Without the existence of homeostasis, life as we know it would be impossible in our constantly changing world!