(introduction...)

Lusaka, 14 September 1999

Summary of the multi-site study*

* The full report of the multi-site study has been submitted for publication.

In many large towns in Central, East and southern Africa the HIV prevalence rate among pregnant women currently exceeds 30%, while in the cities and towns of most of West Africa fewer than 10% of pregnant women are infected. What accounts for these enormous variations? Some urban populations admittedly have a longer-standing epidemic than others, but the time factor alone does not explain all the differences. Clearly, HIV has been spreading at different rates in different populations.

To understand more about this differential rate of spread, a multi-site study was carried out in four African towns with differing HIV prevalence trends in pregnant women. Kisumu (Kenya) and Ndola (Zambia), in Central/East Africa, were selected as the towns with high HIV prevalence, while the low-prevalence towns in West Africa were Cotonou (Benin) and YaoundCameroon).

Between June 1997 and March 1998, surveys were carried out in all four sites to compare:

· sexual behaviour patterns - e.g. age of sexual initiation and marriage, number of sex partners, contacts with prostitutes - which may determine the probability of exposure to an infected partner

· co-factors - e.g. condom use, other sexually transmitted diseases, male circumcision - which may determine the probability of HIV transmission during intercourse.

Ethical approval for the study was obtained from the national ethics committee in each of the countries where the study took place, as well as from other ethics committees. The general population survey in each town aimed at a random sample size of 1000 men and 1000 women aged 15 to 49 years. Households were visited by a team of interviewers and nurses or doctors. The survey of sex workers was preceded by mapping all places where prostitutes could be found and recording the number of sex workers present in each location at the time of the study team’s visit, so that a representative sample of about 300 prostitutes could be selected in each town.

After giving their informed oral consent, study participants were interviewed on their socio-demographic characteristics and sexual behaviour, using a standardized questionnaire, and were asked to give a blood sample and urine sample. HIV testing was done anonymously, but the result was linked to the interview data and to the results of the laboratory tests for HIV and for the presence of sexually transmitted diseases (STDs) including syphilis, gonorrhoea, genital herpes (HSV-2) and trichomonas infection. Study participants who wished to know their HIV serostatus were referred for pre- and post-test counselling and re-testing, free of charge. Study participants with symptoms and/or signs suggestive of an STD were treated.