Human immunodeficiency virus type 1 (HIV-1) is known for its remarkable genomic variability due to (1) the error-prone nature of the reverse transcriptase (RT), which has no proofreading ability and can generate nucleotide substitutions, deletions, and=or substitutions as well as to (2) recombination between different HIV-1 strains. HIV-1 has been classified into three groups: M (major), O (outlier), and N (new, non-M-non O). The M group, which is associated with the pandemic, is subdivided into distinct clades or subtypes (A-D, F-H, J, and K), circulating recombinant forms (37 CRFs have been described so far), and unique recombinant forms (URFs). This extraordinary variability of HIV-1 is associated with various geographic distributions of subtypes and CRFs. Generally, subtype A is the principal HIV-1 subtype found in Central African countries. Subtype B is predominant in the United States, Europe, Australia, and Brazil. Subtype C is prevalent in South Africa, Ethiopia, and India. CRF01_AE is common in Southeast Asia. 1 In spite of limited information on the molecular characterization of HIV-1 in Asian countries, the distribution of HIV subtypes=CRFs appears to be remarkably diverse. In Uzbekistan, intravenous drug users (IDUs) have been found to be infected with HIV-1 subtype A as well as CRF03_AB 2 ; an outbreak of CRF02_AG cases has also been reported in this country. 3 In Kazakhstan, IDUs were reported to have HIV-1 subtype A. 4 In the Islamic countries, Turkey has reported subtypes A, B, C, D, and G as well as F 5 and Lebanon has reported both HIV-1 (subtypes A, B, C, D, and G) and HIV-2. 6 In Yemen, HIV-1 subtypes A, B, C, and D as well as some URFs have been reported. 7 In Pakistan, data show HIV-1 clade A to be prevalent among the IDUs in Karachi. 8
