Molecular epidemiology of a hepatitis C virus outbreak in a hemodialysis unit in Italy.

Hemodialysis patients are at increased risk of hepatitis C virus (HCV) infection. The aim of this study was to investigate a HCV outbreak in a hemodialysis unit using epidemiological and molecular methods. Between April 2003 and October 2003, anti-HCV seronconversion was detected in four patients attending the unit. These cases were added to 10 patients already anti-HCV positive upon admission in the unit. All 14 anti-HCV patients were tested for HCV RNA and HCV genotype. NS5B and HVR1/ E2 genomic regions were amplified and sequenced in all HCV RNA positive patients and phylogenetic analysis was performed. Furthermore, clinical-epidemiological records obtained from all patients were examined. All four patients newly infected harbored genotype 2c. Genotype 2c was also detected in 2 of 10 patients already anti-HCV positive upon admission. Phylogenetic analysis showed that all newly HCV infected patients harbored very closely related viral isolates that clustered together with the 2c isolate found in one of the two 2c chronic infected patients. All HCV-2c infected patients had no other risk factors except hemodialysis. Three of four newly HCV-2c infected patients and the one HCV-2c chronically infected involved in the outbreak received dialysis on the same day and same shift but used different machines. The remaining HCV-2c newly infected patient and one of the above cited three received dialysis on the same day during different shifts but used the same machine. The outbreak was probably due to breaks of infection control procedures although a related-machine transmission cannot be excluded in one of the cases.