A recent outbreak of human immunodeficiency virus type 1 infection in southern China was initiated by two highly homogeneous, geographically separated strains, circulating recombinant form AE and a novel BC recombinant

New outbreaks of human immunodeficiency virus type I (HIV-1) among injectin g drug users (IDUs) are spreading in China along heroin trafficking routes. Recently, two separate HIV-1 epidemics among IDUs were reported in Guangxi , Southern China, where partial sequencing of the env gene showed subtype C and circulating recombinant form (CRF) AE. We evaluated five virtually ful l-length HIV-1 genome sequences from IDUs in Guangxi to determine the genet ic diversity and the presence of intersubtype recombinants. Sequence analys is showed two geographically separated, highly homogeneous HIV-1 strains. B /C intersubtype recombinants were found in three IDUs from Baise City, in a mountainous region near the Yunnan-Guangxi border. These were mostly subty pe C, with portions of the capsid and reverse transcriptase (RT) genes from subtype B. The subtype B portion of the capsid was located in the N-termin al domain, which has been shown to influence virus core maturation, virus i nfectivity, and binding to cyclophilin A, whereas the subtype B portion of RT was located in the palm subdomain, which is the active site of the enzym e. These BC recombinants differed from a BC recombinant found in Xinjiang P rovince in northwestern China. CRF AE strains were found in IDUs from Nanni ng, the capital of Guangxi, and in IDUs from Pingxiang City near the China- Vietnam border. The A-E and BC recombinants were both remarkable for their low interpatient diversity, less than 1% for the full genome. Rapid spread of HIV-1 among IDUs may foster the emergence of highly homogeneous strains, including novel recombinants in regions with multiple subtypes.