A Straight Dope Classic from Cecil's Storehouse of Human Knowledge

Why is winter the season for colds, flu, etc.?

January 31, 1992

Dear Cecil:

What is it with sickness and cold temperatures? Countless times I have heard it said that winter is "cold and flu season." Mom always said to put my hat and galoshes on or I would catch pneumonia or my death of a cold. But I'm no dope. I know disease is caused by germs, not cold. From what I can remember of high school biology (not much), germs don't like cold any more than we do — in fact it kills them. So how come people get sick more often in the winter? Or do they?

Cecil replies:

Seems like a reasonable question, doesn't it? Too bad there isn't a reasonable answer. All the research of the past three decades has succeeded in doing is undermining the old wives' tales about wet feet causing colds and such without putting anything in their place. Here's what we know so far, and it ain't much:

The cold, wet feet, etc., don't make you more susceptible to the common cold. Several researchers, obviously graduates of the Joseph Mengele School of Medicine, had people sit in cold tubs and whatnot for extended periods to see if they'd catch more colds. By and large they didn't.

If anything, long stretches of cold temps mean you'll catch fewer colds, presumably because the germs die off. People who "winter over" at Antarctic research stations seldom get colds except when they host germ-laden visitors from warmer climes.

We don't have indisputable evidence that winter is "cold season." Most cold sufferers don't see a doctor, and no central record is kept of the colds that doctors do hear about.

Winter is flu season, but not always. The influenza pandemic of 1918-19, which killed at least 20 million people worldwide, reached peak virulence in the most of the world during the late spring and summer and topped out in the U.S. in October.

Still, most flu outbreaks peak in January or February. Why? Figure that out and you may be hearing from the Nobel committee. Cecil's mother's theory is that cold "lowers your resistance" to disease. Sounds plausible, but during major outbreaks the winter months typically bring an equally sharp upward spike in flu in all parts of the country. Sure, Chicago gets a little brisk in the winter. But L.A.?

Something besides the cold obviously is at work. Maybe it's that even in southern California during winter folks keep the windows closed and stay indoors more, giving them a chance to exchange more germs. If we want to get really creative we may note that if you want to catch the latest bug there's nothing like going to church, and the one time people are sure to go to church is Christmas. Hence (maybe) the January outbreaks. OK, I'm reaching. But nobody knows for sure.

Respiratory infections, setting aside colds and flu, seem to be more common in winter but some think that's because of misdiagnosis. For example, what may appear to be sinusitis — runny nose, congestion, and so on — in fact may simply a result of "cold stress." Cold stress is a direct bodily response to cold (like shivering, say), not something caused by germs.

Cold stress symptoms can last several days but eventually go away by themselves; so do most respiratory infections. Since most doctors don't send out for tests, there's no telling what the real problem was. Cold stress is most pronounced when the weather changes suddenly, which is when many folks seem to get colds. Maybe they haven't got a cold, they just are cold, if you follow me.

Psychological (as opposed to physical) stress may also play a role. A study published last year in the New England Journal of Medicine reported that the more psychological stress people were under, the more likely they were to get colds. Cecil can personally attest that cold weather and sunless days can be tough on the psyche. So maybe in the interest of stress mitigation you should pop for a week in Puerto Vallarta — and while you're at it, tell that in-your-face boss of yours to take a running jump.

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A Straight Dope Classic by Cecil Adams
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A Straight Dope Classic by Cecil Adams
A Straight Dope Classic by Cecil Adams
A Straight Dope Classic by Cecil Adams
A Straight Dope Classic by Cecil Adams
A Straight Dope Classic by Cecil Adams
A Straight Dope Classic by Cecil Adams
A Straight Dope Classic by Cecil Adams
A Straight Dope Classic by Cecil Adams
A Straight Dope Classic by Cecil Adams

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