Objectives: On September 30, 2001 we had notice of a probable outbreak of hepatitis C virus (HCV) infection in a hemodialysis unit in Ciudad Real (Spain). We conducted an investigation of the outbreak to determine its cause and implement control measures.
Methods: We performed a descriptive study and another analytic study (retrospective cohort study). In the descriptive study, the incidence of HCV infection in the unit between 01/01/98 and 09/30/01 was studied. In the cohort study, 86 subjects were included, of which 18 were infected with HCV during the outbreak. Virologic study was performed, including serology of anti-HCV antibodies, specific IgG avidity study, polymerase chain reaction and phylogenetic analysis of the viral subtypes found.
Results: In the study period, there were 86 patients under treatment in the hemodialysis unit, of which 27 (31.4%) were HCV-positive before 03/01/01. The epidemic curve suggested a common source with secondary cases. Since 1998 only one seroconversion had been documented (in 1999). Statistically significant differences were found only for the variable of dialysis shift. None of the patients who underwent dialysis on the Tuesday-Saturday-Thursday shift exclusively was infected. All cases were genosubtype 4d, which is uncommon in Spain (accounting for 3%), suggesting a common initial source for all cases. Most of the previous cases of HCV in the hemodialysis unit were 1b; three were 4c/4d and one was 1a. The IgG avidity study suggested that not all the cases were infected at the same time, supporting the hypothesis of a common source with secondary spread.
Conclusions: The outbreak of HCV was confirmed, with 18 cases among dialyzed patients in the central unit. The outbreak was caused by the same viral strain, probably due to a common source with secondary person-to-person transmission among the patients.