Risk factors of viral Hepatitis C infection among adults in a northern province, Thailand, 2006.

Background : Since 1998, viral hepatitis C (HCV) infection has been a disease under notification in Thailand (Non A-B since 1982). By the end of 2006, the number of cases reported during the previous three years had doubled (number/year: 270/2003, 396/2004, 407/2005, 734/2006). Majority of cases were diagnosed in Petchabun Province (26.7%). The Bureau of Epidemiology and local health authorities started outbreak investigations in the province aimed at identifying the risk of infection and implementing control measures. Methods : We reviewed HCV reports in the provincial health office and hospital records. Duplicated reports were deleted. A case-control study was conducted using a structured questionnaire. Case was defined as a resident aged 20-60 years and staying in Muang, Lomsak or Lomkao Districts in Petchabun Province during 2006, with laboratory confirmed HCV by RNA detection or ELISA on repeat testing. Controls were randomly selected residents, matched by village, with laboratory confirmed negative for HCV RNA by PCR and antibody by ELISA technique. Results : There were 13, 34 and 36 cases per year in Phetchabun during 2003-2005. Total 45 and 43 met case and control definitions respectively. Among 45 cases, 87% were males and 57% were injection drug users (IDU). Cases were mostly (70%) asymptomatic. Two cases were found to be ELISA negative, but RNA positive. Univariate risk factors included being IDU, male gender, history of shaving by barber and using commercial sex services. Multiple logistic regression revealed that only IDU was associated with HCV infection, with adjusted OR = 12.9 (95% CI = 2.2-75.2). Factors that had dose-response relationship with HCV infection included shaving by barber (p<0.01), irregular condom use (p<0.01) and tattooing (p=0.02). Conclusion : Petchabun Province could be considered as an endemic area for HCV. IDU was the major risk factor for HCV infection in adults. Discordant laboratory results of two cases suggested the need to review the blood screening protocol. The blood bank was informed for the finding. Further study to determine the effects of interferon and antiviral, especially for the treatment of genotype 6 would be benefit to the patients.