Surveillance of HIV type 1 recent infection and molecular epidemiology among different risk behaviors between 2007 and 2009 after the HIV type 1 CRF07_BC outbreak in Taiwan.

The objective of this study was to analyze recent infections and the molecular epidemiology of human immunodeficiency virus type 1 (HIV-1) among different risk groups since the outbreak of circulating recombinant form CRF07_BC among intravenous drug users (IDUs) in 2004 in Taiwan. Phylogenetic analysis was performed using the env and pol fragment sequences amplified from these specimens. The BED IgG capture incidence EIA (BED-CEIA assay) was used to determine recent infections. Among the 683 HIV-1-positive individuals enrolled between 2007 and 2009, 394 (57.7%) were subtype B, 260 (38.1%) were CRF07_BC, 26 (3.8%) were CRF01_AE, two (0.3%) were CRF08_BC, and one (0.1%) was CRF06_cpx. While the percentage of CRF07_BC decreased (58.5-17.9%, p < 0.001) from 2007 to 2009, the percentage of subtype B increased (37.6% to 74.9%, p < 0.001). A concordant decrease in the proportion of recent infections to new infections among IDUs (63.6% to 9.8%, p < 0.001), accompanied with an increase of the proportion of recent infections in MSM (men having sex with men) (22.4-67.1%, p = 0.77) and heterosexual groups (13.1- 23.2%, p = 0.852), was observed. The decrease in CRF07_BC infections and the reduction in the proportion of recent infections among IDUs reflected the success of harm reduction strategies initiated by the government in 2005.