Risk factors for the transmission of hepatitis C

Due to the availability of testing for antibodies to the hepatitis C virus (anti-HCV) and with the use of the polymerase chain reaction (RT-PCR) to detect HCV-RNA, more sensitive and specific measures can be applied to assess routes of HCV transmission. The aim of the present study was to investigate possible risk factors for transmission of HCV.

160 consecutive patients with chronic hepatitis C (mean age 47.1 +/- 14.1 yr) attending a hepatology out-patient clinic were interviewed to identify transmission risk factors. Genotyping of HCV isolates was performed by direct sequencing of RT-PCR products in the 5'-noncoding and the NS-5 region.

The risk factors of HCV infection were as follows: transfusion of blood or blood products 34.4%, intravenous drug abuse 20.6%, heterosexual contact 3.8%, occupational risk 1.9% and tattoo 0.6%. In 62/160 (38.7%) the route of transmission remained unknown. In one HCV-infected couple we analyzed the nucleotide sequences of the NS-5 region of the respective HCV isolates and found almost complete sequence homology (> 97%). The majority of patients with post-transfusional or unknown mode of transmission were infected with genotype HCV-1a and -1b, while in 6/10 patients with previous i.v. drug abuse, genotype HCV-3a was present. We found no evidence that the mode of disease acquisition influences the course of liver disease.

The majority of patients with chronic hepatitis C have a classical parenteral transmission risk factor. In our study, no source of HCV acquisition was identified in 38.7% of patients. It may well be that the major factors in these "sporadic" HCV infections are variations on the known risk factors. However, since the proportion of these cases is rather high, further attention should be on alternative and as yet unclear transmission routes.