RESUMEN
OBJECTIVE: To describe an outbreak of hepatitis C virus (HCV). DESIGN: Retrospective cohort study. SETTING: Outpatient department of a hospital in Rome, Italy. PATIENTS: All 42 patients exposed to ozone therapy by autohemotherapy or intramuscular injection from January to June 2001. METHODS: Epidemiologic investigation, serologic analysis, and virus genotyping. RESULTS: Thirty-one (74%) of the patients agreed to participate in the study. Three (9.7%) had symptoms of HCV infection. This incidence rate was higher than the rate of 1.4 per 100,000 per year in the regional population. Six patients were positive for HCV antibodies and HCV RNA for a prevalence rate of 19.4%, which was much higher than the estimate of 0.9% in the population. Virus genotype 1b was found in two case-patients (one symptomatic) and 2c in four case-patients (two symptomatic), one of whom was known to have an HCV infection since 1986 and could have been the source of infection. The infected patients were all being exposed to ozone-enriched transfusions of autologous blood. Although the specific mode of transmission between patients was not detected, transmission probably occurred during one of the three busiest therapeutic sessions in the 6-month period. CONCLUSIONS: Transmission of HCV infection may occur during medical procedures with limited bleeding. Standard precautions must be applied in any healthcare setting; restricting the number of individuals treated during each therapeutic session could be an effective way of avoiding accidental transmission of infection.