Zimbabwe's epidemic was one of the biggest in the world until the number of people infected with HIV in Zimbabwe almost halved, from 29% to 16%, between 1997 and 2007. Remarkably, this occurred against a background of massive social, political, and economic disruption in the country.
Today's findings strongly show that people in Zimbabwe have primarily been motivated to change their sexual behaviour because of improved public awareness of AIDS deaths and a subsequent fear of contracting the virus. The researchers found that other important drivers have been the influence of education programmes that have shifted people's attitudes towards having multiple concurrent sexual partners in extramarital, commercial and casual relations and that have increased the acceptability of using condoms for casual sex.
Professor Simon Gregson, from the School of Public Health at Imperial College London, and senior investigator on the study, said: "Given the continuing, and worrying, trend for high HIV/AIDS infection rates in many sub-Saharan African countries, we felt it was important to understand why the disease has taken a such a dramatic downturn in Zimbabwe. Very few other countries around the world have seen reductions in HIV infection, and of all African nations, Zimbabwe was thought least likely to see such a turnaround. This is why there was such an urgent need to understand its direct and underlying causes."
Dr Timothy Hallett, also from the School of Public Health at Imperial College London and an investigator on the study, said: "The HIV epidemic is still very large, with more than one in ten adults infected today. We hope that Zimbabwe - and other countries in southern Africa - can learn from these lessons and strengthen programs to drive infections down even further."
The scientists say a change in peoples' attitudes towards their numbers of partners was aided by HIV/AIDS prevention programs organised by the National AIDS Council through the mass media and church-based, workplace-based, and other interpersonal communication activities. The unfavourable economic situation in Zimbabwe from the early 2000s would also have driven down the number of concurrent partners a man could have, due to the constraints on his wallet, but occurred after behaviour had begun to change and would be unlikely to have altered his attitude towards infection. Other underlying factors found to distinguish Zimbabwe from neighbouring countries, and which may have contributed to the changes in behaviour, included its well-educated population and strong traditions of marriage.
The researchers reached their overall conclusions after investigating the results of studies from the last twenty years, which were also considered at a national public health meeting in the Zimbabwean capital, Harare, in 2008. Several other factors affecting HIV/AIDS infection were also discussed, including the age at which people first engaged in sexual behaviour, the introduction of HIV counselling and testing services, and transmission of the virus through means other than sex, such as blood transfusion and needle sharing. However these were ruled out following close examination of the medical and programme evidence.
The results of this study have been extensively and openly debated at the national meeting in Zimbabwe, where attendees reached a 'clear consensus' about the legitimacy of the findings. The researchers hope that, by making the data available more widely, the conclusions of the study can now be judged by other policy makers in the international community and that a clear message can be agreed about the factors driving a decline in HIV/AIDS.
Some of the studies upon which this paper is based were funded by the United Nations Population Fund (UNFPA), which provided some logistical support as well as helping with coordination between the studies. The United Nations HIV-AIDS Program (UNAIDS) and the Zimbabwean Ministry for Health and Child Welfare sponsored this study, along with funding from the Wellcome Trust.