Research finds viruses want to kill men more than women and 'man flu' is a real condition

Scientists have found viruses are more deadly in the male of the species because women are a "more valuable host". Photo / 123RF

Men who fall ill are often mocked by women as weaklings suffering from 'man flu', a not-so-polite term for a condition that exists mainly in their fevered imaginations.

But research suggests it might be time to give ailing chaps the benefit of the doubt, for scientists have found viruses are more deadly in the male of the species because women are a "more valuable host".

Some bugs adapt to cause less severe disease and lower mortality rates in women so they can be passed on to their children during pregnancy, birth and breastfeeding.

This may explain why women suffering from a heavy cold recover more quickly, but it also explains why some viruses are more vicious in men than women and children.

Researchers from Royal Holloway University of London say women are more "valuable" to bugs as an additional route for them to infect more people.

Biologist Dr Francisco Ubeda said: "Viruses may be evolving to be less dangerous to women, looking to preserve the female population."

"The reason these illnesses are less virulent in women is the virus wants to be passed from mother to child, either through breastfeeding, or just through giving birth."

Experts have long believed that the difference in death rates for men and women comes from the different ways in which their immune systems react to infection.

But the latest study, published in the journal Nature Communications, highlights the fact that the HTLV-1 virus causes leukaemia more often in men than women, who are able to pass it on to their children through breastfeeding.

In the Caribbean, where fewer women breastfeed, there is no difference between the sexes who develop HTLV-1 and then adult T-cell leukaemia.

However, the infection is two to three-and-a-half times more likely to develop into this deadly form of leukaemia in Japan, where more mothers breastfeed and do so for longer.

The study also showed men infected with tuberculosis are 50 per cent more likely to die than women, and that those who contract Human Papilloma Virus are five times more likely to develop tonsil cancer.

A man with Epstein-Barr virus, which causes glandular fever, is three times more likely than female victims to develop Hodgkin's lymphoma.

The study says: "It makes evolutionary sense for the pathogen to cause less severe disease in females if they provide more opportunities for transmission than males, making them a more valuable host."

Dr Ubeda added: "Pathogens are adapting to be less virulent in women to increase their chances of being passed on to the next generation during pregnancy, birth and infancy."

Survival of the fittest is relevant to all organisms, not just animals and humans.

"It is entirely probable that this sex-specific virulent behaviour is happening to many other pathogens causing diseases. It is an excellent example of what evolutionary analysis can do for medicine."

The study raises the prospect of defeating viruses that target men more than women by tricking them into thinking they have infected a female.

A treatment that manipulates the cues used by pathogens to determine the sex of their host could switch on the female-only variety, lowering death rates for men.

Co-author Professor Vincent Jansen said: "It has already been established that men and women react to illness differently, but evidence shows that viruses themselves have evolved to affect the sexes differently."

Previous research has shown men suffer more from a high temperature than women when they have flu.