Can Warm Weather Cause the Flu?

Medical experts expose the season's most popular cold and flu myths.

September 17, 2008, 2:52 PM

Jan. 11, 2007 — -- It's hard to tell what spreads faster during cold and flu season -- the viruses, or the myths surrounding them.

And with temperatures in the Northeast reaching record highs for this time of year, many wonder if this midwinter "heat wave" has anything to do with an apparent increase in cold and flu cases.

However, it turns out this speculation may be just another myth -- one of many that resurface every year once the sneezes, sniffles and sick days begin to peak.

"These notions have a life of their own," says Dr. William Schaffner, professor and chair of the department of preventive medicine at Vanderbilt University School of Medicine in Nashville, Tenn.

"Virtually everything we 'know' about getting colds and the flu is myth," says Dr. Neil Brooks, former president of the American Academy of Family Physicians. "The only things that prevent colds are hand washing and/or avoiding contact with other people, and I don't know if hand washing really works."

But though cold and flu myths may not be accurate or scientific, they could represent a completely natural part of how the public deals with some of the unknown aspects of colds and flu.

"Since many aspects of viral immunity are unknown, people may look to these alternative mythologies for an explanation of these phenomena," says Robert Garry of the Tulane University School of Medicine in New Orleans, La.

The science behind nearly every common knowledge tip about colds and the flu is shaky at best, disease experts say.

And yes, that includes this season's conjecture that warmer weather is contributing to an increased spread of cold and flu bugs.

"I know of no scientific information which suggests that warmer weather during the winter increases the chances of spreading influenza," says Stephen Cavalieri, director of microbiology at Creighton University Medical Center in Omaha, Neb.

"After all, it's during the winter months that influenza usually makes its appearance."

In fact, the warmer weather may be having exactly the opposite effect on the spread of respiratory illness.

"The only piece of research I was able to find that attempted to study the relationship of temperature trends and morbidity and mortality, found that warmer weather was associated with a decrease in mortality from influenza," says Dr. Bill Cayley, from the University of Wisconsin department of family medicine in Madison.

He adds that past research shows that for each 1-degree Fahrenheit increase in average temperature, there's a more than 2 percent decline in deaths from pneumonia and influenza.

The idea that exposure to cold weather alone can cause a cold or the flu appears equally flawed.

"Cold weather has no direct affect on the flu virus," Schaffner says. "However, cold weather might drive us all indoors, making it easier for the flu virus to be transmitted from person to person."

"Cold weather can exacerbate cold and flu symptoms -- think mild hypothermia-like effects," Garry says. "But the myth that your mother told you that if you go out without your coat, you'll catch a cold or flu, is false."

"My guess is that people get sick in the winter because they are inside a lot, and visit each other for the holidays, and in the visiting process, spread viruses through coughing and handshaking," says Dr. Michael Fine at Hillside Avenue Family and Community Medicine in Scituate, R.I.

"I suspect the airplane and car are the real means of disease transmission."

Weather is not the only mythical source of the cold and flu. Garry says that many have pointed to sunspots as a culprit, since the last six sunspot peaks have coincided with flu pandemics. He says, however, that there is no relation between the two events.

But while the sunspot myth may be fairly benign, there are other potentially harmful cold and flu misconceptions.

One of these is that you can get influenza from a flu shot.

"There is no truth to it," Schaffner says. "This myth actually prevents many people from getting the influenza vaccine, thus exposing them to the serious infection caused by that virus."

Schaffner adds that the vaccine myth may have arisen from the vaccine used in the 1960s, which was a somewhat cruder version of the vaccine used today.

"Back then, a sore arm and some fever for a day or so was pretty common," he says. "This could have been misinterpreted as flu from the vaccine."

The idea that certain herbal preparations can ward off or lessen the effects of colds and flu may also be counterproductive.

"Many patients who take echinacea for a cold cure find that their nasal and sinus symptoms worsen if they have seasonal allergies to ragweed and pollens due to a cross reaction," says Dr. Clifford Bassett, from the Long Island College Hospital in New York.

"They actually get an allergy attack instead of cold relief. This is known as 'cross reactivity.'"

Even though most myths about colds and flu are unscientific, not all of them are completely baseless.

"Starve a cold, feed a fever is actually a misquoting of the Hippocratic maxim 'if you starve a cold you will have to feed the fever,'" Garry says. "The truth is that you should pay careful attention to nutrition in both cases."

This, he says, could fuel another myth -- the Lenten fare of chicken soup as a cold and flu cure-all.

"Children and elderly people who don't eat during illness are going to do worse," he says. "It makes sense."

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