Next time you feel the flu coming on, think twice before reaching for painkillers: they could do more harm than good. With the flu season underway, millions will be taking flu remedies, which commonly include painkillers. The general medical advice is to take painkillers such as acetaminophen or aspirin. But although such drugs can make you feel better, they also lower fever, which can make the virus itself worse. According to an analysis published last week, painkillers taken to treat fevers could cause 2,000 flu deaths each year in the United States alone. Fever is thought to be an antiviral weapon, because many viruses find it hard to replicate at temperatures above the body’s 98.6 degrees. But research hasn’t made it clear whether relieving fever slows recovery. Some studies show that lowering fever may prolong viral infections and increase the amount of virus we can pass on to others.