The next time you’re feeling feverish from the flu, don’t reach for aspirin or acetaminophen to bring your temperature down. These painkillers could be doing more harm than good in fighting off the infection in your body, according to an evaluation recently published in the science journal Proceedings of the Royal Society and reported by the Washington Post.

The findings estimated that painkillers taken to treat fevers could be increasing both the number and severity of flu cases in the United States—and this could be causing up to 2,000 additional deaths from the flu each year.

That’s because a fever is actually one of the body’s most potent antiviral weapons. Many viruses find it hard to replicate at temperatures above 98.6 degrees, and when the immune system senses a viral invasion, it naturally raises the body’s temperature to kill these germs.

“Fever won’t hurt” a patient combatting the flu, said Edward Purssell, PhD, MSc, a doctor at King’s College in London, who agreed with the report, “and it might help.”

Purssell and other researchers cited several studies that show lowering a fever during the flu can actually prolong the length of infection and also increase the amount of flu virus we can pass on to others.

After evaluating one study to find out how much more of the virus people produce when their fevers are suppressed, and how many cases of the flu this could cause, scientists found that painkillers could increase flu transmission by up to 5 percent each year. This could result in 700 to 2,000 extra flu deaths.

Experts also say painkillers could make people feel better when they aren’t actually well, leading them return to work or school while still infectious, which of course would spread the flu even more.

Want a drug-free way to combat the flu this winter? Click here to read more.