Fever-reducing pills may help spread flu, Canadian study warns

A woman sick with the flu blows her nose while resting at home. File / Global News

TORONTO – If you reach for medication to take the edge off of a fever when you’re sick with the flu, a new Canadian study warns that move may be helping you produce even more germs.

It sounds counterintuitive: you’re taking pills to feel better. But McMaster University scientists say these fever-reducing medications could lead to tens of thousands of more flu cases.

“Most people take them because they feel lousy. You want to feel better and they address the symptoms that you have,” researcher Dr. David Earn told Global News.

“It turns out that when you reduce your fever, the amount of virus that you give off is more than you produce when you have a fever. That’s going to be surprising to most people,” Earn said.

He’s a mathematics professor at the university’s Michael G. DeGroote Institute for Infectious Disease Research where he specializes in using mathematical models to understand infectious disease and patterns of epidemics.

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Studying how these fever-reducing drugs could affect a population

In this instance, Earn and his colleagues looked at how drugs affect flu. They include ibuprofen, acetaminophen and acetylsalicylic acid – or Advil, Tylenol and Aspirin as most people know them.

“Because fever can actually help lower the amount of virus in a sick person’s body and reduce the chance of transmitting disease to others, taking drugs that reduce fever can increase transmission,” Earn said.

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He suggests that fighting the fever with drugs could lead to a five per cent increase of flu cases, and 1,000 additional deaths from the flu across North America.

That’s based on a mathematical model he built taking into account how much of the population takes drugs when they have the flu, how many encounter a fever, and what the increase in viral shedding might be, among other factors.

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Earn suggests that based on swabbing the noses of sick patients, people with the flu who took meds to get rid of their fever increase their amount of virus by 70 to 80 per cent.

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Most flu viruses replicate better at lower temperatures. But staving off a fever could also mean that people sick with the flu might try to head outdoors, to work or to run errands, and in turn, infect others, Earn said.

Fevers are also your immune system’s natural reaction to fighting the influenza. As your body’s ramping up to fight the flu, the fever stalls how quickly the virus multiplies.

Leading Canadian infectious disease experts say that the findings are “thought-provoking” but not necessarily enough to convince patients to stow away their fever-reducing meds while nursing the flu.

Should this dissuade you from taking these meds when you’re sick with the flu?

Dr. Allison McGeer, director of infection control at Mount Sinai Hospital, says that the mathematical model doesn’t necessarily take into account how many people are actually taking fever-reducing meds. It’s also hard to tell how much virus these people shed and if they feel well enough to leave their homes.

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Studying these intricacies could be expensive and hard to do.

“The whole dynamic of when people stay away from other people when they’re ill is very complex and there’s a huge number of missing pieces in it,” she told Global News.

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But these models are meant to study scenarios that wouldn’t be easy to track in real life, Dr. Michael Gardam, University Health Network’s director of infection prevention and control, said.

“[The findings] are thought-provoking. It’s not wrong or right, they simply have limitations. They’re mathematical models so they’re not looking at the true complexity of the situation, but they make you think about how diseases are transmitted,” Gardam said.

Gardam said that if patients are sick with the flu and want to take fever-reducing meds, he wouldn’t stop them. But flu patients tend to stay home instead of heading to the doctor’s office, McGeer notes.

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READ MORE: Should flu shots be mandatory for health care workers?

Filling in the gaps

What Earn hopes to study next is how often flu patients will mix with others after taking these drugs to suppress their fevers. How much more likely are they to head to work or to school after taking a pill to lessen their fever? Knowing this could paint a clearer picture in estimating how frequently viruses spread through these carriers.

But Earn says his findings, published Tuesday night in the Proceedings of the Royal Society B, should not dissuade doctors or patients from taking these medications while they’re sick with the flu.

Earn just hopes his findings offer awareness to readers, he said. “Be aware that you can be more infectious. Stay home until you’re over the infection, it’s very easy to prevent the effect. There’s an effect on other people,” he said.

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