|Connecting Lower HIV Infection Rates with Changes in Sexual Behaviour in Thailand - Data collection and comparison (UNAIDS, 1998, 18 p.)|
|Linking epidemiological patterns with behaviour|
Cohort studies have, then, confirmed evidence seen in cross-sectional studies indicating that the Thai epidemic has been driven predominantly by risky sexual behaviour. They have also confirmed that the number of new infections dropped in people who cut down on risky sexual behaviour or never started it.
· Consistent links in the north
Because HIV status can reflect risk taken many years before, behavioural change will not translate instantly into lower HIV prevalence. Even with that in mind, a pattern of lower risk behaviour and HIV prevalence is compellingly drawn by a study of 21 -year-old military conscripts in the severely affected northern region of Thailand. As Figure 5 shows, less commercial sex and greater use of condoms was followed by lower STD and HIV rates across the northern region. In an attempt to understand how much HIV infection in 21 -year-olds is related to risk behaviour engaged in before the start of behavioural change, the same study looked separately at infection rates in those of the 1995 cohort of conscripts who began their sexual lives after 1992 (when the 100% Condom Use Campaign was in force). The study found that these men were only one-tenth as likely to be HIV positive as men in the cohort as a whole.
Other comparisons of data from independent sources also confirm that STD and HIV prevalence mirror behaviour across the country:
· The decline in STD rates reported from government clinics in nine randomly selected provinces largely mirrored the decline in the number of commercial sex encounters reported in surveys in those same provinces.
· As non-use of condoms with commercial sex workers became less common across the country throughout the early 1990s, so did the number of cases of STDs reported by government clinics (see Figure 6).
· HIV prevalence in conscripts from various regions reflected the levels of unprotected commercial sex reported by men in those regions, except in the north.
Figure 5. Behavioural change and HIV/STD decline among 21-year-old men in the north
Source: Nelson et al., 1996
In the north, HIV prevalence was far higher than the level predicted by levels of unprotected commercial sex. It is worth noting that the epidemic in the north appears to be older than that in other areas of Thailand, perhaps due to greater incidence of injecting drug use in that region. The virus began spreading widely before behavioural change became common. In other provinces, by contrast, people began adopting safe behaviours before the virus began its explosive growth. Indeed, it is very encouraging to note that in Thailand, behavioural change in most areas occurred long before the effect of the epidemic (in terms of AIDS-related deaths) was seen.
Figure 6. STD rates decline along with non-use of condoms
Source: VD Division, Epidemiology Division, Ministry of Public Health, Thailand