Fever-reducing meds encourage spread of flu: McMaster report

Taking over-the-counter flu medication and going into work or school when you are sick with the flu is exactly what doctors tell you not to do. Now, a group of McMaster researchers are saying the same thing. And they have numbers to show just staying home and getting better will save lives.

Staying home when sick with flu backed by mathematical model

Despite the study's findings, recommendation remains the same – get vaccinated and stay home when you have the flu, Bolker says.

Taking over-the-counter flu medication to cut your fever might help you feel better, but it might not be so good for the people you come into contact with.

A new study by McMaster University researchers published in the Proceedings of the Royal Society predicts that individuals who take medications with fever-reducing ingredients and then have contact with others are encouraging transmission of the influenza virus.

"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," said lead researcher David Earn, a professor of infectious disease and mathematics. 

After crunching numbers, the researchers realized that avoiding medications with ibuprofen, acetaminophen and acetylsalicylic acid and just staying home could save many lives. Their research estimates as many as 1,000 lives across North America each year could be saved.

"We put together a chain — how many people have influenza, how many of them take these anti-fever drugs, how much does that increase the amount of virus they give off, how much does that increase the chance that they’re going to affect somebody else, how much does that increase the overall size of the seasonal flu epidemic," said Ben Bolker, professor of math and biology.

"When you put all those numbers together, the answer you get is it increases the size of the annual influenza epidemic by about five per cent."

That sounds like a small percentage, but considering the number of people who contract the flu on an annual basis, it’s actually very significant.

"The influenza epidemic is huge — it’s millions of people," he said. "Five per cent is a lot."

Add in the number of deaths related to the flu — about 40,000 a year in the U.S. alone, Bolker said — and that number becomes even more significant.

"Given the way we put all these numbers together, it looks like if nobody took anti-fever when they got sick with influenza, the number of cases would go down five per cent, presumably the number of deaths would go down five per cent, and that’s a lot of cases and a lot of deaths," he said.

Bolker cautions that there is uncertainty in the numbers, largely because studying how the flu transmission works is hard to do — it would require isolation and very careful attention paid to contact.

Medical advice for fever

The team, Bolker said, hopes doctors or public health professionals take notice of the numbers presented and go forward with clinical trials.

But what this study does is add more caution.

"The thing we’re adding to the current set of recommendations is you might want to be extra careful," Bolker said. "If you really care about reducing the number of cases or deaths, you should reduce contact."

The study opens the door for more research to see if giving fever-reducing medications in humans truly has an effect on how much virus is transmitted to the next person, said Dr. Jesse Pappenburg, an infectious disease specialist at Montreal Children's Hospital.

But he said the findings go against medical convention when it comes to whether an individual patient should be taking over-the-counter medications for fever and cough.

"If the fever stopping you from being able to get out of bed and having that cup of soup to help you feel better, well then go ahead and take that over-the-counter fever medication," Pappenburg said.

Not reducing fever, especially in young children, may have potential harmful effects for children who become dehydrated and need to go to the emergency department, he said.