Videos and memes mock men for overreacting when they catch an everyday illness. But is there a biological reason for men’s behavior?

According to the Cambridge Dictionary, man flu is “an illness such as a cold that is not serious, but that the person who has it treats as more serious, usually when this person is a man.”

According to the farcical Urban Dictionary, man flu is “more painful than childbirth.”

Of course, man flu, which has been parodied online for years, is not a diagnosable affliction, and it goes without saying that not all men become helpless fatalists when they have run-of-the-mill sniffles, while some women do.

But experts say at the heart of the joke are some fascinating immunological differences that exist between the sexes — not only in humans, but also in some other species.

“There is something to the idea that men and women, males and females, suffer the effects of infection differently,” said Marlene Zuk, a professor of ecology, evolution and behavior at the University of Minnesota.

There is strong evidence that men are more likely to experience severe infections than women are when they get sick. This was seen in the early days of the Covid pandemic, when men had higher hospitalization and death rates. The same was true during the 1918 flu pandemic, when many more men than women died.

Some of this could be explained by behavior, said Dr. Matthew Memoli, a principal investigator at the National Institute of Allergy and Infectious Diseases. Research finds that, in general, men take fewer precautions to avoid getting sick, such as wearing a mask or washing their hands. Men also tend to engage more in unhealthy behaviors, like smoking or drinking alcohol, and they are more reluctant to seek medical care, all of which can lead to worse outcomes when they do fall ill.

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