9th Conference on Retroviruses and Opportunistic Infections Seattle, Washington - February 24 -February 28, 2002

Conf Retroviruses Opportunistic Infect 2002 Feb 24-28;9:abstract no. 18
C. Kuiken, U. R. Smith, D. Lang, and T. Bhattacharya
Los Alamos Natl. Lab., NM

BACKGROUND: The subtype C epidemic is the fastest-growing and for that reason the most dangerous sub-epidemic of HIV-1. Tracing its spread around the world can help decide which vaccine best suits which region.

METHODS: Phylogenetic trees were used to analyze the evolution of the subtype C epidemic. The year of origin of the African and Indian subtype C epidemics were estimated using methods refined by Korber et al.

RESULTS: Only a few African subtype C form clear subclusters and few inferences can be made from them. However, in Ethiopia the availability of a large number (>250) of samples from several cities has led to the identification of a distinct local subtype C sub-clade. The introduction of subtype C into Ethiopia was dated to the early 1980s, concordant with epidemiological data. The recent origin of this sub-epidemic may have contributed to the ease with which the Ethiopian sub-epidemic could be traced. In Asia, the subtype C epidemic shows clear epidemiological patterns. The variant that is spreading in India is distinct from all African sequences. Another sub-epidemic is seen in south-central China, driven by drug use and drug trafficking. A third distinct sub-epidemic, clearly branching off from the Indian subtype C, is currently invading Nepal. Reports of subtype C infections emanate from other countries surrounding the Golden Triangle (Myanmar, Vietnam, Thailand, Cambodia), but few subtype C sequences are available from those regions. Our estimate for the beginning of the Indian subtype C sub-epidemic is 1986 (95% CI 1973-1988), which is consistent with epidemiological data. The best estimate for the origin of subtype C in Africa (1933, 95% CI 1571-1967) is more problematic, because due to the scarcity of longer sequences from early strains it is heavily influenced by a few data points. More early samples are needed before a more stable estimate can be obtained.

CONCLUSIONS: While in Africa the overall pattern in the subtype C epidemic appears to be chaotic, there are regions where distinct sub-epidemics can be identified. It is possible that patterns will emerge when the sampling density increases. The Asian epidemic is probably much younger (dating from the mid-1980s) and tracing the spread of the virus here appears to be very feasible. While the number of well-annotated sequences is small, increased awareness and interest in designing an appropriate vaccine should lead to a rapid accumulation of data.

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Copyright © 2002 - Foundation for Retrovirology and Human Health. Reproduction of this abstract (other than one copy for personal reference) must be cleared through the Foundation for Retrovirology and Human Health. Licensed (AIDSLINE) from National Library of Medicine.