ICAAC: Sharp decline in HIV prevalence reported in pregnant women in rural northern Zimbabwe

A dramatic 41% decline in HIV prevalence has been reported in pregnant women in Zimbabwe, according to the latest survey done in this population. The results were reported in a poster presentation at the 47^th Interscience Conference on Antimicrobial Agents and Chemotherapy in Chicago this week.

Previous studies have suggested that HIV prevalence is on the decline among adults in Zimbabwe. This study only looked at pregnant women presenting to the Salvation Army Howard Hospital in the Mazowe district of rural northern Zimbabwe, but dramatically confirmed this decline in prevalence among these women.

The Mazowe district is home to 270,000 residents, the vast majority of whom are subsistence farmers. The economy is in crisis with a 3700% inflation rate and currency collapse; there is very little infrastructure to support services. An antiretroviral scale-up programme which began in September 2004 has 1060 patients enrolled, 888 of whom were alive at last report. A stable medication supply is available for only 200 patients.

All women receiving antenatal and postnatal care at Howard Hospital between August 1999 and August 2007 were offered the option of voluntary HIV counselling and testing. More than 80% of the women accepted HIV testing, a rate which has remained stable. This is the largest sampling ever of Zimbabwean women in a single study. Testing was initially done via 2-step ELISA; rapid testing became available after 2002.

The investigators presented data on 15,555 women tested, of whom a total of 3.121 tested HIV-positive. Analysis showed that HIV prevalence amongst pregnant women was declining in a linear fashion by 1.4% per month (95% CI: 1.1 – 1.7% per month).

During the eight year observation period, prevalence dropped from 26.6% (95% CI: 24.2 – 29.2%) to an estimated mean of 15.6% (95% CI: 13.1 – 18.1%). This represents a 41% drop in estimated prevalence from the original rate, which began as early as 1999, and continues through to August 2007.

In comparison, HIV prevalence among pregnant women in South Africa has declined only slightly in the past two years after a long pattern of increase, and still remains close to 30%.

Discussing the possible reasons for this decline, the researchers note that “although a natural fall in the HIV epidemic curve through patient deaths may explain the observed decrease, decreased sexual "mixing" due to decreased disposable income of working class men, and collapse of transportation infrastructure may be relevant." The researchers also note that incidence rates – the rates of new infections – were not assessed.

Local prevention programmes include voluntary counselling and testing, condom distribution campaigns, community education including puppet shows and AIDS clubs for students, and mother-to-child prevention programs. However, "it is unclear if [these] local education, prevention programs and behaviour change are likely to have also contributed to this trend.”

But a review of the evidence on changes in HIV prevalence in Zimbabwe carried out by an expert group for UNAIDS in 2005 concluded that it was prevention activities – particularly condom promotion and partner reduction – starting from the mid-1990s, that had contributed most to the decline in HIV prevalence in Zimbabwe since 2000.