Who infects whom? Migration and the HIV epidemic in South Africa

High rates of population movement fuel the spread of HIV in Southern Africa. Urban migrants returning home to their rural communities can help drive the epidemic. However, is this migration pattern the main cause of the spread of infection within rural communities? The South African Medical Research Council investigated this issue in Hlabisa, a rural district of KwaZulu/Natal.

The most common migration pattern is for men to move ontheir own to urban centres in search of work, leaving partners and families inrural areas. It is usually assumed that men become HIV-positive while away fromhome and infect their rural partners when they return.But is this true in the context of South Africa's mature epidemic?

The researchers looked at HIV rates among 98 migrant and 70non-migrant couples in the district, where 62% of adult men spend most nightsaway. They found that:

• One in five adults is HIV-positive - 24.4% ofmen and 15.5% of women.
• HIV infection is more common in younger couples,those with an earlier sexual debut and couples where one partner has had asexually transmitted infection (STI) in the last four months.
• In 70% of couples, neither partner is infected,whereas both are HIV-positive in 9%. In one fifth of couples, only one partneris infected. The man is the infected partner in 71.4% of these ‘discordant’couples.
• Migrant couples are more likely than non-migrantcouples to have one or both partners infected and to be HIV discordant.

The researchers used data to develop a mathematical model toestimate the relative risk of becoming infected from inside compared to outsidea regular relationship and found that:

• Migrant men are 26 times more likely to beinfected from outside their regular relationships than from within. The figurefor non-migrant men is 10%.
• Women are also more likely to be infected fromoutside their relationship than they are by their husband, whether or not he isa migrant.

These results show that migration is a risk factor for thespread of HIV not just because men return home and infect their rural partners.Women – whether partners of migrants or non-migrants – are actually more likelyto become infected from outside their primary relationships. But women withabsent husbands more commonly have additional sexual partners, which puts themat higher risk.

Migrant men are clearly at high risk of infection and needtheir own targeted interventions. But programmes are also needed in ruralareas. There should be a specific focus on situations in which one partner isalready infected in order to protect the uninfected partner. Strategies couldinclude:

• couple counselling
• more aggressive STI treatment
• antiretroviral therapy for HIV-infected partners
• education messages aimed at couples
• development of more family-friendly housing nearthe mines
• rural development,including better economic opportunities, that would allow men not to have tomigrate.