|Differences in HIV spread in four sub-Sharan African cities (UNAIDS, 1999, 9 p.)|
Prevalence of HIV infection
The prevalence of HIV infection in men (aged 15-49) was 3% in Cotonou, 4% in Yaound20% in Kisumu and 23% in Ndola. For women, the respective prevalence rates were 3%, 8%, 30% and 32%.
In all sites, except Cotonou, overall prevalence was significantly higher in women than in men. The largest male/female divergence was found among 15-19-year-olds in Kisumu and Ndola. In Kisumu, over 3% of male teenagers were infected, compared with 23% of female teenagers. In Ndola, HIV prevalence in this age group was 4% in boys and 15% in girls.
The prevalence of HIV infection among sex workers was extremely high in the two high-prevalence sites (Kisumu, almost 75%; Ndola, 68%) compared with Yaound33%), although the prevalence in Cotonou (over 57%) was also quite high. Across these four sites 40% of the prostitutes were 24 years old or younger, with a figure of 56% in Ndola. Almost a quarter of prostitutes in Ndola were under 20.
In the two low-prevalence sites and in Kisumu, more than 70% of circulating HIV-1 strains belonged to subtype A. In Ndola practically all circulating strains were subtype C. The biggest range of strains was see in Yaoundwhere subtypes A, D, E, F, G and H were found, as well as strains belonging to group O.
Sexual behaviour characteristics
Sexual debut and marriage
In all sites, between 97% and 99% of men and of women 20 years old and above reported having had sexual intercourse. However, among 15-19-year-olds the proportion of those who were sexually active ranged from under 50% in Cotonou to just over 70% in Kisumu. For both males and females, age at first sexual intercourse was lowest in Kisumu and highest in Cotonou. Significantly more girls in Kisumu and Ndola had their sexual debut before age 15 than in the two low-prevalence sites.
The percentage of men and women who were currently-married or ever-married was significantly higher in Kisumu and Ndola than in the low-prevalence sites. Similarly, age at first marriage was significantly lower for both men and women in Kisumu and Ndola than in Cotonou and Yaound
Rate of partner change
The highest rate of partner change was found in Yaoundwhere men reported an average of 10 lifetime partners (compared with 5 in Kisumu and 4 in Cotonou and Ndola) and women reported 3 (compared with 2 in the other three sites). Never-married men and women in Yaoundeported the largest numbers of non-spousal partners in the year preceding the interview, followed by men and women in Kisumu. Currently-married men in the high-prevalence sites reported fewer non-spousal (extramarital) partners than married men in Cotonou and YaoundExtramarital relationships were reported by very few currently-married women (1-3%) except in Yaoundwhere 12% of women reported at least one such relationship in the year before the interview.
Age mixing between non-spousal partners
Age differences between non-spousal partners were similar in Cotonou, Yaoundnd Ndola, but significantly smaller in the high-prevalence site, Kisumu. The age difference between non-spousal partners, as reported by men, was 4 in Cotonou and Yaound3 in Kisumu and 4 in Ndola, the male partner always being older. However, among married - teenage girls living in Kisumu and Ndola, the older their husband (and the larger the age difference between the partners), the higher their risk of being HIV-infected.
Male contacts with sex workers
The proportion of men reporting at least one contact with a sex worker in the past year was almost 7% for Cotonou, 13% for Yaoundalmost 7% for Kisumu and 11% for Ndola. When analysis was restricted to men who reported having non-spousal partnerships in the year before interview, the percentage having contact with a prostitute was significantly higher in Ndola (over 32%) than in Cotonou and in Kisumu (around 15%) and Yaoundalmost 20%).
While HIV prevalence among sex workers tended to be higher in the high-prevalence sites, as mentioned earlier, the HIV rate in Cotonou sex workers was also quite high. However, use of a condom with the most recent client was reported more often by sex workers in Cotonou than in any other site. Of the HIV-infected sex workers in Cotonou 64% reported condom use with their last client, compared with 349% in Yaound50% in Kisumu and 30% in Ndola. When the data on HIV prevalence and condom use with clients are examined together, it is clear that sex work clients in Ndola and Kisumu are more exposed to HIV infection than clients in the low-prevalence towns.
A relatively low proportion of men in all sites - ranging from 21% in Cotonou to 25% in Ndola - reported that they often or always used condoms with non-spousal partners. Women in the low-prevalence towns reported less condom use than women in the high-prevalence sites.
Co-factors in HIV transmission
Syphilis, an STD that causes genital ulcers, was by far most prevalent in Ndola, followed by YaoundSerologic evidence of current or previous genital herpes (HSV-2 infection) - another ulcer-producing STD - was more common in the high-prevalence sites than in the other two sites. Taken together, the prevalence of the two ulcerative STDs was higher in the towns with high HIV prevalence. The differences between the sites were especially marked among young people under 25. In all four sites HSV-2 infection was strongly associated with an increased risk of HIV infection in both men and women.
The prevalence of gonorrhoea was generally low and variable. Chlamydial infection was more common in younger age groups, especially in girls, and the highest prevalence was in Yaoundfollowed by Kisumu. The highest rates of trichomonas infection were found in women in Kisumu and Ndola (29% and 34%).
In Cotonou and Yaoundearly all men reported being circumcised, while in Ndola only 10% of men were circumcised. In Kisumu, where the overall percentage of circumcised men was less than 30%, HIV prevalence was below 8% in men circumcised before their sexual debut and 25% in uncircumcised men. In multivariate analysis, being circumcised was associated with a lower risk of HIV infection.