Scientists at McMaster University say the widespread use of medications that contain fever-reducing drugs could be leading to tens of thousands more influenza cases, and even more than 1,000 possible flu-related deaths, in North America each year.
The findings, published in the journal Proceedings of the Royal Society B, say fever reducers like ibuprofen, acetaminophen, and acetylsalicylic acid could actually make flu sufferers more contagious. The thinking is that a fever actually lowers the virus levels inside the body. If you suppress that mechanism, you become more of a reservoir for spreading the disease.
Beyond that, taking fever-easing drugs could suppress your symptoms enough so that you head back to school or work while you're still contagious.
"People often take—or give their kids—fever-reducing drugs so they can go to work or school," says lead study author David Earn, PhD, professor of mathematics at McMaster University. "They may think the risk of infecting others is lower because the fever is lower. In fact, the opposite may be true: The ill people may give off more virus because fever has been reduced."
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The Canadian researchers used flu data from human and animal studies and then crunched it in a mathematical model to see how the increase in the amount of virus given off by a single person taking fever-lowering drugs could increase the number of cases in a typical year. The bottom line? They say fever suppression increases the number of annual cases in North America by about 5 percent. That makes sense, since a fever is the body's natural response, a defense mechanism that protects others and us.
But hold the phone, says flu expert William Schaffner, MD, professor of preventive medicine at Vanderbilt University School of Medicine in Nashville.
"The study is basically a clever and provocative 'thought experiment,'" he says, noting the authors make some assumptions and use a rather elaborate mathematical model to come up with their conclusions.
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"They have no human data to show that the use of anti-fever medications, such as Tylenol, actually increase influenza virus shedding and transmission. I'm dubious about several of their assumptions, but even granting them their point—they may well, in the end, be correct—I do not think that fever-reducing meds contribute meaningfully to flu transmission," Dr. Schaffner says.
He points out two issues:
1. Flu is very readily transmitted already. It's hard to imagine that rate could be enhanced much more.
2. The study discounts transmission during the day before the person becomes ill. "The data clearly show that people are infectious for at least 24 hours before they become sick," he explains. "It is during this period that the flu virus is spread so readily."
Dr. Schaffner says doctors will continue to recommend fever-reducing meds, and patients will continue to take them because they make them feel better.
"The only way to reduce transmission risk is to stay home when you are sick, avoid getting close to others, and to take antiviral meds such as Tamiflu, which will reduce the duration and severity of the illness and reduce the production of new flu viruses," he says.
As always, people with underlying conditions that put them at an increased risk of flu complications like pneumonia, hospitalization, or death should contact their doctor as soon as they become ill. Antivirals are most effective when started early on. Older adults, weak people, those living with diabetes or heart or lung disease, or people who are immunocompromised, pregnant, or obese face a higher risk of flu complications.
For more on easing flu symptoms, read 25 Foods That Fight Cold & Flu.