Molecular epidemiology and forensic genetics: application to a hepatitis C virus transmission event at a hemodialysis unit.

Molecular phylogenetic analyses are frequently used in epidemiologic testing, although only occasionally in forensics. Their acceptability is hampered by a lack of statistical confidence in the conclusions. However, maximum likelihood testing provides a sound statistical framework for the testing of phylogenetic hypotheses relevant for forensic analysis. We present the results of applying this method to a small hepatitis C outbreak produced in a hospital hemodialysis unit that involved 6 patients. Polymerase chain reaction products from a 472-nt fragment of the E1-E2 region, including the hypervariable region, HVR-1, of the hepatitis C virus genome were cloned, and an average of 10 clones/patient and from 11 additional control patients were sequenced. The method allows a statistical evaluation that the likelihood of each sample belonging or not to a given group, a question of relevance in many forensic and epidemiological analyses of molecular sequences.