Research Article: A Surprising Prevention Success: Why Did the HIV Epidemic Decline in Zimbabwe?

Date Published: February 8, 2011

Publisher: Public Library of Science

Author(s): Daniel T. Halperin, Owen Mugurungi, Timothy B. Hallett, Backson Muchini, Bruce Campbell, Tapuwa Magure, Clemens Benedikt, Simon Gregson

Abstract: Daniel Halperin and colleagues examine reasons for the remarkable decline in HIV in Zimbabwe, in the context of severe social, political, and economic disruption.

Partial Text: While dramatic gains in the availability of antiretroviral medications in developing countries have been achieved [1], there is growing consensus that, unless prevention efforts can be made more effective, there will ultimately be no victory in the fight against HIV/AIDS [1]–[4]. Maintaining tens of millions of people on treatment throughout their lifetimes will not be sustainable or affordable, particularly as drug resistance may increasingly result in the need for much more expensive second and third line medications. Although there have been promising breakthroughs in a few other areas, notably male circumcision and prevention of mother-to-child transmission (PMTCT) [1],[2],[5], it is widely recognized that behavior change must remain the core of prevention efforts [2]–[4].

HIV prevalence in Zimbabwe increased rapidly in the early to mid-1990s, before reaching a plateau in the late 1990s (peaking at an estimated 29% adult prevalence in 1997 [13]), and declining after 2000 (down to 16% estimated prevalence in 2007). Mathematical modeling fitted to surveillance data [14] (Figure 1A) estimates that HIV incidence peaked around 1991 and (as in many other African countries [21]) declined gradually thereafter, mainly as part of the natural course of the epidemic, primarily due to saturation of infection in high-risk populations [11],[14],[22]. Between about 1999 and 2003, the pace of incidence decline accelerated considerably, which empirical data [13],[14] and modeling [14] suggest corresponded to reduced levels of risky sexual behavior.

In fact, the prevalence of other STIs was greatly reduced during the early 1990s, mainly due to widespread syndromic management services [15]. Although STI control remains an important public health measure, the data from clinical trials regarding the population-level impact on HIV incidence are increasingly unconvincing (Text S1) [2],[24]. However, it has been hypothesized that STI treatment during the early phases of an HIV epidemic may help to reduce transmission (although this is unconfirmed by observational evidence; e.g., given the absence of HIV declines in several other African countries that had also implemented early and aggressive STI control programs). Reported condom use increased steadily during the 1990s (reaching 59% among men for last non-marital sexual encounter in the 1994 DHS), but did not increase further between 1999 and 2005/6 (Figure 1B), and remained very low for regular partnerships [13]. However, there is some evidence for modest improvement in the consistency of condom use among women in casual partnerships [13],[16], a more important measure for reducing infection risk than reported use at last sex [9].

One question arising from this review is why similarly high AIDS mortality and extensive coverage of HIV prevention programs (resulting in similarly high levels of reported condom use, early and large reductions in STI incidence, etc.) in several other countries in the region have not yet led to substantial declines in HIV prevalence (or multiple sexual partnerships) [3],[7],[9],[21]. Our comparative analysis of eight southern African countries revealed few patterns of association. The HIV epidemic in Zimbabwe is somewhat older than in some other countries in the region, yet HIV prevalence has been declining markedly for over a decade now, which has not occurred to nearly the same extent, for example, in Malawi and Zambia (where HIV arrived even earlier). In addition to the severe economic decline, where Zimbabwe does stand out is in having high levels of both secondary education and marriage, especially in urban men, among whom the greatest level of behavior change evidently has occurred [13],[15],[19] (Figures 2, S1). It appears that this unique combination helped facilitate: 1) a clearer understanding and acceptance of how HIV is sexually transmitted (once such information became widely available through various AIDS education and prevention programs commencing in the early 1990s [15]), as some studies of schooling levels and HIV determinants have suggested [27] and 2) a greater ability to act upon “be faithful” messages, given the stronger marriage pattern [28]–[30] in Zimbabwe than that in neighboring countries also having relatively well-educated populations, such as Botswana and South Africa.

The behavior changes associated with the HIV decline in Zimbabwe appear to have resulted primarily from increased interpersonal communication about HIV and its association with risky sexual behavior, due to high personal exposure to AIDS mortality and correct understanding of sexual HIV transmission (due to relatively high education levels along with information provided by HIV communication programs), as well as the deteriorating economic situation. However, the substantial shift in social norms that appears to have occurred, such as STI infection having become a cause for shame, suggests that the economic decline was probably more a co-facilitating factor rather than the major reason for behavior change; e.g., reduced income may prevent men from frequenting bars, but wouldn’t change their attitude about having an STI.