Simplified phylogenetic tree for viruses in different host
species. Dashed lines show estimated times when viruses diverged
from one another, finding their way into a new group of hosts. (Data:
Hon et al., 2008)Schmidt’s trial was the first time that phylogenetic analysis had
been used in a US criminal case. Since then, the methods have
appeared in other cases around the world. Following a surge in
cases of hepatitis C in Valencia, Spain, police investigators linked
many of the patients to an anaesthetist named Juan Maeso.
Phylogenetic analysis confirmed he was the likely source of the
outbreak, and in 2007 he was convicted of infecting hundreds of
patients by reusing syringes.[5] Genetic data has also helped prove
innocence. Shortly after the Maeso case, a group of medics were
released from a prison in Libya. They’d been held for eight years
after accusations that they’d deliberately infected children with .
The group were freed in part because of phylogenetic analysis,
which showed that many of the infections had occurred years before
the team had arrived in the country.[6]
As well as pointing to the likely source of an outbreak,
phylogenetic methods can reveal when a disease arrived in a
particular location. Suppose we are investigating a virus like ,
which evolves relatively quickly. If the viruses circulating in an
area are relatively similar, it suggests they haven’t had long to
evolve, so the outbreak is probably quite recent. In contrast, if there
is a lot of diversity among current viruses, it means that there has