Monitoring hepatitis C infection in a major Swedish nephrology unit and molecular resolution of a new case of nosocomial transmission.

Hepatitis C virus (HCV) infection is a frequent problem in hemodialysis units. The prevalence and incidence of HCV infection over a decade were studied in a nephrology unit affected by previous nosocomial HCV transmission. The HCV non-structural 5B protein gene was sequenced to achieve phylogenetic analysis of a new (incident) case of infection. Proportions of patients who were and were not infected with HCV remained similar over the period, as did the inflow and outflow of patients infected previously. In 1997, 12/157 (8%) of patients at the unit (treatment: hemodialysis, peritoneal dialysis, and renal transplant recipients) were positive in HCV RNA, whereas in 2007 the overall number was 9/239 (4%). One patient acquired an HCV infection, and the NS5B sequence in that case clustered with genotype 2b sequences found in patients from an earlier outbreak. Comparing the HCV from the incident patient with several stored longitudinal samples and cloned PCR products from the most likely source patient revealed close phylogenetic relationship with an HCV quasispecies member from the possible source. The source patient and the incident newly infected patient were not scheduled on the same dialysis shift, although the records showed that simultaneous treatment occurred on two occasions during the months preceding transmission. In conclusion, over the 10-year period, the proportion of HCV-infected patients at the unit was unchanged. Only one new infection occurred, which originated from a fellow patient's quasispecies. This establishes phylogenetic analysis as a valuable tool for tracing patient sources of HCV transmission.