Migration and the transmission of STIs

Historically migration has been associated with the spread of ideas, artifacts, knowledge, and, less favorably, disease. This last, dramatically witnessed with the importation in the fifteenth century of small pox to the New World, resulted in dire consequences for the indigenous population [1]. A few hundred years later, small pox was introduced to Australia both in 1780 and 1870, and was a major cause of Aboriginal deaths [2]. With such grave effects it is perhaps no wonder that migration has been intuitively associated with spread of diseases through communities and that migrants are associated or even “blamed” for the spread of disease. More recently, there are reports of South Africans blaming migrants from Zimbabwe for spreading HIV [3, 4]. In any population, the spread of infectious disease depends on the rate of contact between susceptible and infectious individuals [5] and migration provides an important mechanism by which that can continue to happen. However with a sexually transmitted infection (STI) it is not movement and mixing alone but also changes in sexual behavior concomitant with migration that determine the impact on the potential level of disease spread.