sex workers, 1.9% for patients with sexually transmitted infections, and 6.7% for men who have sex with men in saunas or bath houses. Since then, the number of people living with HIV-1/AIDS in Taiwan has jumped sharply, from an 11% increase in 2003 to a 77% increase in 2004 and a 123% increase in 2005. However, after the implementation of a harm-reduction program, a 10% decrease was seen in 2006. The current estimated number of HIV-1/AIDS cases in Taiwan is about 30,000, which suggests that the infection rate there could be greater than that in China: 30,000 per 23 million (1/767) compared with 650,000 per 1.3 billion (1/2000). A risk-factor analysis of reported cases showed that the proportion of intravenous drug users infected with HIV-1 increased from 1.7% (13/772) in 2002, to 8.1% (70/862) in 2003, to 41.3% (628/1520) in 2004, to 72.4% (2461/3399) in 2005, and dropped to 68.6% (2017/2974) in 2006. The most important risk factor for Taiwanese intravenous drug users is needle-sharing, followed by the sharing of heroin diluents. A molecular epidemiological study showed that more than 95% of intravenous drug users with newly diagnosed HIV-1 in 2004 and 2005 were infected with CRF07_BC, a circulating recombinant form of subtypes B' and C. Previously, several studies suggested that CRF07_BC originated in China's Yunnan province as a mix of subtype B' from Thailand and subtype C from India. The subtype is believed to have moved to Xinjiang in China's northwest along a major heroin-trafficking route. Of the 60,000–100,000 injecting drug users in Taiwan, 10–15% may be infected with CRF07_BC. If so, they probably represent the largest group of such intravenous drug users in northeast Asia. The circulating recombinant form might have followed a separate drug-trafficking route to Taiwan from Yunnan via southeast China, Guangxi, and Hong Kong. There have been enormous increases in the amount of heroin smuggled into Taiwan and in the number of intravenous drug users since 2002, when five intravenous drug users from southern Taiwan were diagnosed as the country's first HIV-1 seropositive cases infected with CRF07_BC. Even though the Hong Kong authorities identified three cases of CRF07_BC infection in 2001, a serious outbreak in that city's population of intravenous drug users is believed to have been blocked by a methadone maintenance program. Monitoring Close monitoring of emerging HIV-1 subtypes related to intravenous drug use and implementing harm-reduction programs has been and continue to be