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The Viral Path

Using molecular phylogenetics, a group of Spanish researchers were able to trace a hepatitis C virus outbreak back to an anesthetist, contributing to his conviction.

As Fernando González-Candelas from the University of Valencia and his colleagues report in BMC Biology, they sequenced the NS5B and E1-E2 viral regions from 322 HCV-1a-infected patients and 44 local controls. They then compared those regions to those from the presumed source. Forty-seven patients were excluded, as their infections appeared to result from a local source rather than the presumed source of the anesthetist.

In addition, as the infection date for a handful of patients was known, the researchers could develop a molecular clock to estimate the time of infection for the other patients. Indeed, González-Candelas traced the outbreak back to more than a decade before its detection.

"[W]e used the fast evolutionary rate of HCV to disentangle a large and complex transmission process from a single source to almost 300 recipients spanning over a decade, a period during which the infecting viral population underwent evolutionary changes itself," the researchers write. "The process was further complicated by two additional issues: a large number of potentially affected patients, several of which might have been infected by HCV from alternative, unidentified sources, and the need to provide individual rather than population-based statements about the likelihood of having been infected or not from the presumed source in a court setting."

In an associated commentary, the University of Leuven Anne-Mieke Vandamme and Oxford University's Oliver Pybus note that the Spanish researchers' work was used to "support other lines of evidence" and not establish guilt.

"The estimation and interpretation of viral phylogenies are inherently uncertain and therefore they should be used in court very differently to DNA fingerprints," they add.

BioMed Central's Biome notes that the anesthetist was sentenced to about 2,000 years in prison.