Molecular epidemiology of a hepatitis C virus outbreak in a haemodialysis unit

Background. Haemodialysis patients are at high risk of infection by hepatit is C virus. The aim of this study was to investigate a hepatitis C virus ou tbreak which occurred in a haemodialysis unit, using epidemiological and mo lecular methods. Methods. Five seroconversions to hepatitis C virus antibody (anti-HCV) were observed over a 6 month period and these were added to the four previously recorded anti-HCV-positive patients. All nine patients involved in the out break were tested for HCV RNA by reverse transcription-polymerase chain rea ction and hepatitis C genotype determination was accomplished by a reverse hybridization assay. Furthermore, part of the NS5 region of hepatitis C gen ome (nucleotide positions 7904-8304) was amplified and sequenced in all HCV RNA-positive patients. Then, phylogenetic analysis of the nucleotide seque nces obtained was carried out in order to investigate any possible epidemio logical linkage among patients. Detailed epidemiological records were also available for all haemodialysis patients. Results. Samples from all five incident cases and three out of four prevale nt HCV infections were found positive for HCV RNA. HCV genotyping studies r evealed that all incident cases were classified as 4c/d, whereas one and tw o prevalent cases were la and 4c/d respectively. Sequence comparisons and p hylogenetic tree analysis revealed that six of the patients harboured very similar strains and clustered together, including all incident and one prev alent case, which was implicated as index case. Further epidemiological ana lysis was consistent with patient to patient transmission. Conclusions. Molecular and epidemiological analysis suggested that horizont al nosocomial patient to patient transmission was the most likely explanati on for the virus spread within the haemodialysis unit under study.