Rapidly Spreading of hepatitis C virus among injecting drug users in the Philippines - Implications for HIV epidemics Shortened title: Rapid HCV spreading in the Philippines

From the trends of human immunodeficiency virus (HIV) epidemics in South and Southeast Asia, it was postulated that an HIV epidemic would start as a bloodborne infection among injecting drug users in the Philippines. In 2002, 560 individuals were recruited in Metro Cebu, Philippines and tested for HIV, hepatitis C virus (HCV) and hepatitis B virus (HBV) infections. Seroprevalence of anti-HCV among injecting drug users (70.1%, 61/87) was significantly higher than those among inhalation drug users (16.3%, 7/43; P=0.00; OR=12), sex workers (0%, 0/130; P=0.00; OR=∞), antenatal clinic attendees (0%, 0/100; P=0.00; OR=∞), and students/health care workers (2.0%, 4/200; P=0.00; OR=115). Seroprevalence of HBsAg among injecting drug users (10.3%, 9/87) was significantly higher than those among sex workers (2.3%, 3/130; P=0.01; OR=4.9), and antenatal clinic attendees (3%, 3/100; P= 0.04; OR=3.7), but was not statistically different from those among inhalation drug users (9.3%, 4/43; P=0.9) and students/health care workers (4.5%, 9/200; P=0.06). None of the study population was reactive to anti-HIV antibody. The HCV strains obtained from the injecting drug users belonged to either genotype 1a or 2b and the strains in each genotype clustered closely to each other. There was no dual infection with genotype 1a and 2b. These suggest that the HCV infection in injecting drug users may be rapidly emanating from limited source individuals in Metro Cebu, Philippines.