People sick with the flu often take medication to alleviate the accompanying fever. But their relief may come at a price for others: New findings suggest that suppressing fever can result in the infection of tens of thousands of additional people each flu season.
Fever, though unpleasant, can actually be beneficial. The condition can lower the amounts of virus in a sick person's body, because viruses replicate less efficiently in higher temperatures. Fever can also help immune responses work better.
In a new study, researchers used mathematical models to find the effects of widespread use of medications that suppress fever. They found that in a typical flu season, fever-reducing drugs such as ibuprofen and acetaminophen may lead to tens of thousands of additional influenza cases, along with more than a thousand deaths attributable to influenza, across North America.
"When they have flu, people often take medication that reduces their fever. No one likes to feel miserable, but it turns out that our comfort might be at the cost of infecting others," said study researcher David Earn, a professor of mathematics at McMaster University in Ontario, Canada.
"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. "We've discovered that this increase has significant effects when we scale up to the level of the whole population."
The practice of reducing fever goes back centuries, even before the advent of fever-reducing drugs. Alexander the Great, suffering from a mysterious illness that would lead to his death in 323 B.C., was advised to take cool baths to treat his fever, the researchers said.
However, much as the overuse of antibiotics resulted in the rise of drug-resistant bacteria, widespread use of fever-reducing drugs may not be as harmless as is commonly thought — both by the average person and within the medical community, the researchers said. [5 Scariest Disease Outbreaks of the Past Century]
"People are often advised to take fever-reducing drugs, and medical texts state that doing so is harmless," said Paul Andrews, researcher at the Department of Psychology, Neuroscience and Behavior at McMaster. "This view needs to change."
More flu cases
The researchers used information from various sources, including previous studies on humans and on ferrets, which provide one of the best animal models for studying influenza. The scientists then used a mathematical model looking at the increase in the amount of virus given off by a single person taking fever-reducing drugs; the model computed how much that increase would, in turn, increase the overall number of cases of flu. They modeled this for both a typical seasonal flu and a year when a new strain of influenza has caused a flu pandemic.
The results suggested that for seasonal influenza, suppressing fever can result in a 5 percent increase in the number of influenza cases and deaths. This would correspond to more than 1,000 additional deaths from influenza in a typical year across North America, according to the study. For a pandemic, the model predicts a 1 percent increase.
The researchers said future experiments need to determine the precise increase in virus levels in the body associated with fever reduction. Studies are also needed to estimate the increase in disease spread from sick people who took fever-reducing drugs that made them feel better, allowing them to go to school or work when they should have stayed home.
"People often take, or give their kids, fever-reducing drugs so they can go to work or school," Earn said. "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."
The study was published yesterday (Jan. 21) in the journal Proceedings of the Royal Society B.