Abstract
Genetic diversity of the HIV-1 envelope gene has shown a steady increase over time in the Thai and other regional epidemics. A serial survey of subtype CRF01_AE polymerase gene (RT) diversity in Thailand was performed, using 48 novel and 15 reported sequences covering the period 1990--2000. These sequences were gathered from individuals whose sole risk factor for infection was heterosexual contact. By contrast to envelope, diversity was low and, despite a 40% increase early in the epidemic, has remained static since 1996. These results indicate that epidemic HIV-1 may be constrained within defined limits of genetic diversity at least in some genomic regions.