Researchers found that untreated moderate fever helped fish clear their bodies of infection rapidly, controlled inflammation and repaired damaged tissue. “We let nature do what nature does, and in this case it was very much a positive thing,” says immunologist Daniel Barreda, lead author on the study and a joint professor in the Faculty of Agricultural, Life & Environmental Sciences and the Faculty of Science.

Moderate fever is self-resolving, meaning that the body can both induce it and shut it down naturally without medication, Barreda explains. The health advantages of natural fever to humans still have to be confirmed through research, but the researchers say because the mechanisms driving and sustaining fever are shared among animals, it is reasonable to expect similar benefits are going to happen in humans.

That suggests we should resist reaching for over-the-counter fever medications, also known as non-steroidal anti-inflammatory drugs, at the first signs of a mild temperature, he says. “They take away the discomfort felt with fever, but you’re also likely giving away some of the benefits of this natural response.”

The study helps shed light on the mechanisms that contribute to the benefits of moderate fever, which Barreda notes has been evolutionarily conserved across the animal kingdom for 550 million years. “Every animal examined has this biological response to infection.”

For the study, fish were given a bacterial infection and their behaviour was then tracked and evaluated using machine learning. Outward symptoms were similar to those seen in humans with fever, including immobility, fatigue and malaise. These were then matched to important immune mechanisms inside the animals.

The research showed that natural fever offers an integrative response that not only activates defences against infection, but also helps control it.The researchers found that fever helped to clear the fish of infection in about seven days — half the time it took for those animals not allowed to exert fever. Fever also helped to shut down inflammation and repair injured tissue.

“Our goal is to determine how to best take advantage of our medical advances while continuing to harness the benefits from natural mechanisms of immunity,” says Barreda.