What Makes Flu Seasonal?

Just as flu season gathers force here in the northern hemisphere, it’s petering out in the southern half of the globe. No matter where you are, you’re more susceptible to the flu in the winter months. Even if, let’s say, some research physicians expose you to live flu virus in the middle of summer, you’re still less likely to get sick than if the same doctors hit you with the same virus in the dead of winter. Why? One big risk factor for flu infection is a lack of vitamin D. We naturally produce vitamin D when we’re exposed to sunlight, and as the days shorten in the winter, we produce less and less of it. That led these researchers to think that flu epidemics could be a sign of widespread vitamin D deficiency, due in part to decreased solar radiation. So it seems darkness makes the flu go ’round. (HT: Jason Tetro) [%comments]