DEMOGRAPHIC-IMPACT OF THE HIV EPIDEMIC IN THAILAND

Objective: To assess the impact of the HIV epidemic on the demographic development of the Thai population. Methods: A deterministic mathemat ical model was used to predict simultaneously epidemiological and demo graphic processes. Partial differential equations express the relation ships between biological, behavioural and demographic variables. The m odel allows the evaluation of different sexual mixing patterns, variab le transmission probabilities and incubation times. Validity analysis was performed by generating antecedent HIV prevalence patterns among m ilitary recruits and pregnant women. Results: On the national level in Thailand we predict that the cumulative number of people in Thailand with HIV infection will exceed 1 million by 1999; the number of deaths from AIDS will be 550 000 by the year 2000 but will not reach 1 milli on until after the year 2014. Without the HIV epidemic the population growth rate was estimated at 1.3% per annum until 1995, after which a decline to 0.9% by 2005 is predicted. The HIV epidemic started to affe ct the population growth rate by 0.026% per year in 1991, and the diff erence is predicted to rise to about 0.12% per year during the period 1995-2000, to decline to 0.06% in 2005 and then to disappear. In the m id-1990s HIV affected mainly the 15-35-year-old age group, but over ti me younger and older age groups have been affected as a result of peri natal transmission, and a decline in fertility as well as ageing of th e 15-35-year-old birth cohort. Because of HIV, in 2000 there will be 6 12 000 (1%) fewer people than expected and by 2010, 1 140 000 fewer (1 .6%). We predict that the demographic impact of the HIV epidemic in th e northern region will follow the same pattern, but with greater sever ity. Here, the effect on the population growth rate and the population age distribution is likely to be twice as high as at the national lev el. Conclusions: It is estimated that 1 million Thais will be infected with HIV by the year 2000 and an almost equal number will have died o f AIDS by the year 2014. Although these numbers seem high, their direc t and indirect effects on the demographic structure of the Thai popula tion are small. However, at a regional level, for example in the north ern region, the effect of the HIV epidemic may be more severe. (C) 199 8 Lippincott-Raven Publishers.