|Connecting Lower HIV Infection Rates with Changes in Sexual Behaviour in Thailand - Data collection and comparison (UNAIDS, 1998, 18 p.)|
Thailand established a sentinel surveillance system for HIV in 1987, early in the epidemic. Beginning in 14 provinces and rapidly expanded across the country, the system was able to determine levels of infection in various vulnerable and general population groups: sex workers, male STD patients and IDUs as well as pregnant women and blood donors.
Another important source of epidemiological information is the anonymous-unlinked testing of 60,000 21 -year-old men chosen each year as military recruits. Selection of recruits is by lottery, so the group is relatively representative of young men across the country.
Data about other STDs also offers useful corroborating information about HIV, since these diseases are largely transmitted by sexual activity. If people are curtailing or modifying the behaviours that expose them to HIV - principally unprotected sex with partners whose sexual history may include risk behaviour - we would expect to see a drop in new cases of other STDs as well as of HIV.
Data on HIV gathered through cross-sectional monitoring - that is, testing of a certain population at single points in time - can be validated with longitudinal cohort studies that follow individuals over time to determine how many become infected within a certain period. In Thailand, such studies are available for a number of different groups, including repeat blood donors.