Sexual Relationships and Pathogen Evolution

The reading by Nahmias and Nahmias from earlier this month detailed the wide breadth of influencing factors that played a role in the spread of sexually transmitted infections (STIs) throughout human populations all over the world. Although the connection between sexual activity and disease was established a long time ago, the epidemiology behind STIs continues to be ever multi-faceted, making the development and execution of successful interventions very difficult. The paper also explained how the nature of the transmission allows for interesting trends in the evolutionary paths taken by the infectious agents. Many factors were cited as contributing to the spread of STIs, including travel, ecological change, economic inequality and public health issues, among many others, all of which created a complex web of interrelationships in the disease epidemiology.

The article “Love and Sex Influence Disease Evolution” talks about a study from August 2006 in The American Naturalist that examined in detail one of those particular influences on sexually transmitted pathogens. The scientists that authored the study, Eames and Keeling, concluded that the length of time sexual partners stay together has a significant influence on the evolution of multiple strains of a particular infection. It showed that some strains evolve as better suited for monogamous pairings with little chance of a rapid change in host environment (considered slow strains because they have the ability to persist in a host for a long time), while others are better adapted for short term relationship (considered to be fast strains because they cannot utilize resources in order to persist in one host). The study gives further proof for why different strains of a single infection can exist without selecting against each other.

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