Forensic epidemiologists track rapid viral mutations to convict disease-spreading criminals
In May 2012, a hospital in the town of Exeter, New Hampshire, reported a cluster of hepatitis C cases that were apparently related. Four patients were diagnosed shortly before and the tests showed that the genetic code of the virus strains in their bodies is almost identical. Since the hepatitis C virus (HCV) mutates rapidly, disease researcher Jose Montero concluded that the infections originated in the same person. "It was clear that we had to find this person immediately," says Montero, the state's director of public health.
The four patients also had a shared history: three were treated in the cardiac catheterization laboratory at Exeter Hospital and the fourth worked there. When the researchers began to examine patients who had been treated before in the same laboratory, they located another 29 cases. Montero's colleagues at the State Public Health Laboratory sequenced the genomes of the viruses from that outbreak and built an evolutionary tree that led them to David Kwiatkowski who worked at the lab. The police believe that Kwaitkowski injected himself with narcotics and used the same syringes to treat patients.
Increasingly, scientists are helping to solve crimes using molecular methods originally developed for epidemiological purposes: tracking the spread of disease in large populations. In a similar case of using forensic epidemiology, Fernando González Candelas of the University of Valencia helped track an even larger outbreak of hepatitis C in Spain in which an anesthesiologist was suspected of infecting hundreds of patients.
Kendall's research group compared the genetic sequences of the virus strains that caused the outbreak and other strains of HCV that were common in Valencia. The researchers found that the patients infected in this outbreak carried a virus that was remarkably close to the virus carried by the anesthesiologist, more so than any other virus that was common in the community at the time, which almost certainly indicated that the doctor had infected them. Kendalls and his colleagues were also able to determine when the patients became infected and determine that the infection occurred while they were under the doctor's care.
The researchers recently published in the journal BMC Biology The details of the investigation that led in 2007 to the conviction of the anesthesiologist for infecting 275 people. "People can live a long time with HCV and infect a large number of people," says Kendalls. "The only way to prove they are the source is through forensic epidemiology."
Despite the increase in the use of forensic epidemiology in court, the method has limitations. One of the criticisms is that the creation of the viral genetic tree involves some degree of interpretation and evaluation. Critics warn that jurors can give the science unjustified certainty "and fail to fully understand the complexity of the method and its inherent shortcomings."
The New Hampshire jaundice case never went to a jury. After Montero and the FBI built a criminal case that revealed the trail of HCV infections and the transfer of drugs across several US states, Kwiatkowski pleaded guilty in August 2013. Although Montero could not say with certainty why Kwiatkowski accepted the plea deal, "I would like to believe it was due to the strength of our epidemiological investigation."
The article was published with the permission of Scientific American Israel
