British scientists find out why certain viruses are more lethal for men than women

Scientists Find Out Why Viruses Are More Lethal For Men Than Women-1

Scientists have long struggled to uncover the reason why certain viruses are more lethal for men than women. Males, for instance, are nearly 1.5 times more likely to die of tuberculosis than females, and a staggering five times more susceptible to cancer in case of human papillomavirus (HPV) infection than the other sex. According to a new study, this happens because women are indispensable as hosts, making their survival essential to the spread and transmission of pathogens. Speaking about the find, Francisco Úbeda of the Royal Holloway University of London said:

Viruses may be evolving to be less dangerous to women, looking to preserve the female population. 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.

As pointed out by the researchers, the main aim of any kind of pathogen, like virus or bacteria, is to multiply and move from one host to another, without actually making them ill. The ailment that often accompanies such infections is usually more of a side effect than the primary objective of the invading microorganisms. Vincent Jansen, one of the members of the research team, explained:

[Illness] is not something a pathogen particularly sets out to do, because it’s shooting itself in the foot, should it have one.

Women, according to the scientists, are valuable as hosts because they are capable of spreading the infection through different means: contact either sexually or otherwise, pregnancy, childbirth or even breastfeeding. As opposed to that, men can transmit these pathogens via a single mode. To understand why certain disease-causing microbes favor women over males, the team turned towards the pathogens’ strategy, instead of focusing on patient response. Úbeda went on to say:

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. We took the ‘pathogen’s eye view’, and researched whether natural selection would favor a different behavior in each sex.

The scientists developed a special mathematical model demonstrating the spread of infection between males and females. For the research, they focused on the human T-cell lymphotropic virus type-1 (or HTLV-1), commonly found in West Africa, Japan and the Caribbean. Recently published in the Nature Communications journal, their study revealed that this infection is approximately 3.5 times more likely to result in the deadly Adult T-cell Leukemia (ATL) in case of Japanese men than women.

In the countries of the Caribbean region, however, the likelihood of acquiring such a disease is equal among the two sexes. It is important to note that HTLV-1 transmission occurs sexually or from mother to child through breastfeeding. Given that breastfeeding practices differ greatly in Japan and the Caribbean nations, that could explain the discrepancy in transmission of the pathogens. Úbeda was reported saying:

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.

Another example involves the Epstein-Barr virus, which is twice more likely to cause Hodgkin’s lymphoma in men than women. Males, the researchers state, are also more susceptible to chickenpox than females, thus confirming the team’s findings since both of these pathogens are capable of spreading from mother to child. However, one question remains. How does the virus actually distinguish between a man and a woman? Jansen added:

We could try to make the virus think it’s in a female body rather than a male body and therefore take a different course of action.

At present, the scientists are examining how different viruses affect the two sexes in case of animals, starting with retroviruses that are responsible for causing cancer in chickens. The team said:

When flocks of chickens are infected with a particular virus, we see that more of the male chickens develop tumors than females.

Source: Royal Holloway University of London

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