Viruses May Have Evolved To Target Men Harder Than Women

There’s at least one part of the world where men don’t have it easier than women but you have to go down to the microbial level to find it.

A new theory put forth in the scientific journal Nature Communications, “The evolution of sex-specific virulence in infectious diseases,” claims that some viruses go easier on women than men. The reason being that like all living organisms, viruses want to survive and by having a less lethal effect on women, they are more likely to be transmitted to another person through childbirth or breasfeeding.

The paper’s authors, Francisco Úbeda and Vincent Jansen of the Royal Holloway University of London, point to several examples such as men with tuberculosis are 1.5 times more likely to die than women.

“Viruses may be evolving to be less dangerous to women, looking to preserve the female population” Dr. Úbeda writes. “The reason why these illnesses are less virulent in women is that the virus wants to be passed from mother to child, either through breastfeeding, or just through giving birth.”

Does that mean legends of the “man cold” are true? Not necessarily. And any perceived differences in how genders react differently to illness could stem from a number of other factors, some psychological and not just purely physiological.

But how could something seemingly as basis as a pathogen know the difference in gender between a male and a female? After all, none of these viruses are exclusive to a single gender. Úbeda and Jansen point out that there many simple and obvious chemical or hormonal differences produced by the body that would make it easy for a virus to “know” what kind of host it has attached itself to. Though Jansen points out that no virus is explicitly “trying” to kill or even hurt a host, that it’s simply a result of the virus replicating itself. “That’s not something a pathogen particularly sets out to do because it’s shooting itself in the foot, should it have one,” he said.

What’s more, the authors say that the process of targeting one gender over the other could be continuing to evolve, showing that natural selection leaves it mark at the highest and lowest levels of nature’s spectrum.

“Survival of the fittest is relevant to all organisms, not just animals and humans,” said Dr Úbeda. “It's entirely probable that this sex-specific virulent behavior is happening to many other pathogens causing diseases. It’s an excellent example of what evolutionary analysis can do for medicine.”