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Modelling 'man flu'

24 March 2010

Research published this week in Proceedings of the Royal Society B shows that there may be some very good reasons why ‘man flu’ has evolved.  Olivier Restif – a Royal Society University Research Fellow – and Professor William Amos at the University of Cambridge have developed a model showing why differences between male and female responses to infection might have evolved.  Critically, this is the first such model to take an ‘ecological’ approach to the way that pathogens and their hosts interact by accounting for the effect that immunity has on pathogens and vice-versa.

The differences between male and female responses to infection are well-documented, with previous research showing that males tend to be more exposed to infection risk than females and that once infected, they tend to suffer more severe symptoms for longer than females.  While popular imagination puts this down to ‘man flu’, the researchers point out that some of these observed effects are rather counter-intuitive from an evolutionary perspective: why would men evolve lower immunity when their behaviour means that they are more likely to be exposed to infection?

This paradox – amongst others – led the researchers to develop a more nuanced approach to modelling the differences in infection response between the sexes.  The authors point out that previous approaches have tended to neglect the dynamic relationships between pathogen and host.  This is a serious omission because the benefits of immunity will clearly be affected by, for example, the prevalence of pathogens in the environment.

While this model is based on a pathogen that transmits via direct contact between two hosts, the authors suggest that further work could be done on developing a similar model to account for sexually transmitted diseases and ‘vertical transmission’ from mothers to babies.  This could provide valuable insights into the transmission dynamics of viruses such as HIV, as well as providing new insights in other areas: “We believe our framework will prove both versatile and flexible enough to be used in a range of future studies on sexual host species.”