Hepatitis C virus infection among dialysis patients in Tunisia: incidence and molecular evidence for nosocomial transmission.

In order to study the incidence of hepatitis C virus (HCV) infection in Tunisian haemodialysis patients and detect its nosocomial transmission, 395 patients were enrolled in a prospective study (November 2001-2003). HCV serological and virological status was determined initially using, respectively a third generation ELISA and an RT-PCR qualitative assay. The genotype of the HCV isolates was determined by sequencing NS5B region. The issue of nosocomial transmission was addressed by sequencing the HVR-1 region of the E2 gene. About 20% of the patients had anti-HCV antibodies and HCV-RNA was detected in 73% of the anti-HCV positive patients. Two cases of de novo HCV infection were identified in two dialysis centers, during virological follow-up of patients susceptible to HCV infection. The incidence of de novo HCV infection was 0.5%. Determining the genotypes in the first center disclosed that all HCV-positive patients were infected with genotype 1b; sequencing of the HVR-1 region of the E2 gene provided strong evidence that the isolate from the newly infected patient and another infected dialysis patient were closely related, confirming nosocomial contamination. The investigation of the second center is pending. Besides, one patient with negative HCV serology had detectable HCV-RNA at the beginning of the study. This case had HCV genotype 1b, two other infected dialysis patients in the same unit had HCV genotypes 4k and 3a; thus precluding nosocomial transmission. Thanks to molecular and phylogenetic methods, one case of nosocomial HCV transmission in haemodialysis was confirmed. Epidemiological investigation suggested nosocomial transmission via the medical and/or nursing staff.