Genetic Mutations Betray a Criminal

A year and a half ago, the hospital in Exeter, New Hampshire, was struck with an outbreak of hepatitis C. Four people were infected with the hepatitis C virus, also known as HCV, three of which were patients of the same department while the fourth worked there.

It was an unusually high number for the small, 100-bed hospital, and the fact that all the patients were linked to the same department told epidemiologist Jose Montero that something was fishy about the situation. Luckily, he knew that HCV’s genetic code mutates quickly and predictably. Montero and his colleagues knew they could find patient zero—the first patient infected in the outbreak—by tracing mutations in the rapidly changing HCV genome.

The FBI says reused needles spread hepatitis C to unsuspecting patients.

That bit of detective work led them to David Kwiatkowski, who the FBI believes fed his narcotic habit using the hospital’s needles, which he later reused on patients, spreading his infection to unsuspecting patients.

It wasn’t the only such case solved that way. Montero and his peers are increasingly sought after in these cases. Here’s Carrie Arnold, reporting for Scientific American:

In a similar application of forensic epidemiology, Fernando González Candelas of the University of Valencia helped to retrace an even larger outbreak in Spain, where an anesthesiologist was suspected of spreading HCV to hundreds of patients.

Candelas’s group compared the genomes of viruses contracted in the outbreak with those of other HCV strains circulating in Valencia. The researchers found that people sickened in the outbreak carried a virus that was significantly closer to the anesthesiologist’s strain of HCV than anything going around in the community, indicating that the doctor had almost certainly infected them. Candelas and his colleagues were also able to estimate when a person became infected to confirm that the infection occurred while that person was under the doctor’s care.

It’s all thanks to a keen understanding of genetics. Not only are we able to better grasp the biology of viruses like hepatitis C, we’re also able to apply that knowledge in unexpected—but decidedly useful—ways.

To learn more about modern forensic science, watch "Can Science Stop Crime?"