The Strange Reason Men Might Get Sicker Than Women

A photo of the H5N1 or "bird flu" virus as seen through a microscope

A photo of the H5N1 or bird flu virus as seen through a microscope | AFP/Getty Images

We don’t worry about major disease outbreaks like we used to. Sure, there are scares related to a certain virus here and there, like Zika or Ebola, but these are largely contained to specific geographic areas. Though they do kill, it’s nothing compared to the plagues humanity has survived in the past. Think of the Black Plague, for example, which killed 25 million people in the 1300s. An outbreak of that magnitude would be unimaginable today.

Though modern medicine and public health policy have managed to help us deal with outbreaks, we still have a lot to learn. When it comes to viruses specifically, scientists are still trying to figure out exactly how they tick. They’re not really alive, yet they can hijack other living cells to reproduce. The more you learn about them, the stranger and creepier they get.

New research has added another layer of strangeness to viruses. As it turns out, they may actually employ certain strategies depending on their host. Specifically, viruses may kill a male host while keeping a female host alive. So, if you’re male, you may have a higher chance of getting a viral infection or even being killed by a virus than a female.

A living-dead microscopic killer carefully selecting its victims? Sounds more like a horror movie villain than anything. Yet, we’ve lived side-by-side with viruses for all of human history.

What makes men more susceptible to a virus

A man fighting off a nasty virus

A man fighting off a nasty virus | iStock.com/IPGGutenbergUKLtd

Getting to the point: Why are men more susceptible to viral infections than women? Or why are they more likely to be killed by a virus? A new study published in Nature Communications says the simple answer is because women can pass along a viral infection to offspring. So, viruses and pathogens may have evolved to be less deadly to the female sex in order to propagate. “Because women can transmit pathogens during pregnancy, birth, or breast-feeding, pathogens adapt, evolving lower virulence in women,” the study reads.

Sorry, fellas. But women are simply more valuable to these little monsters because of their ability to give birth and, thus, reproduce more of the little monsters themselves. It’s evolution at work, even if it is thoroughly unsettling.

But the research team still has work to do. One of the study’s authors, Francisco Ubeda from Royal Holloway University, tells ResearchGate the team tried to think like a pathogen, rather than a patient, to come to its conclusion. “We were surprised that all potential explanations to the observed differences in virulence between men and women were centered on the patient, and that the pathogen had largely been ignored,” he said. “We took the ‘pathogen’s eye view’ and researched whether natural selection would favor a different behavior in each sex.”

Fighting disease

Petri dish with disease growing on it

Petri dish with disease growing on it | iStock.com/solarseven

Ubeda explains to ResearchGate the team’s studies looked at cultural and geographic differences as well. They studied a specific virus (which causes Leukemia, HTLV-1) that is common in Japan, the Caribbean, and parts of Africa. The team found the same virus has adapted to different reproduction methods depending on its surroundings.

“HTLV-1 is between two and 3.5 times more likely to cause leukemia in Japanese men than women,” he said. “In the Caribbean, however, the likelihood of HTLV-1 progressing to leukemia is roughly equal in men and women. This could be because a higher proportion of Japanese women breastfeed their children, and for longer, when compared to women in the Caribbean. This provides the disease more of chance to be passed on to children.”

Obviously, there’s more work to do. But the team’s findings are definitely noteworthy and provide an inside glimpse at natural selection. Viruses are one of the world’s more unique features. This study helps us understand them on a more fundamental level, though. Still, it’s quite weird that a non-living, flying piece of code can seemingly make decisions about who it will or won’t kill. Weird, but fascinating.