Phylogenetic trees, which provide information about evolutionary relationships, can aid epidemiological analyses of disease transmission.

Researchers used an HIV-1 model to systematically evaluate the phylogenies associated with different transmission histories. Transmission can occur directly from one person to another, indirectly through at least one intermediate, or via a common source.

The authors found that transmission histories predict phylogenetic relationships, which can be used to identify the direction of transmission, whether transmission was direct or indirect, and whether a common source was likely.

The authors found that 20 or more genetic sequences per individual typically provided robust results, but the probability of successfully reconstructing the transmission direction was greatly reduced when only a few sampled clones were available or if the donor was infected only for a short time.

The authors analyzed three real transmission histories and confirmed that these histories supported the theoretical evaluations. The study demonstrates how phylogenies can be used to reconstruct transmission events.

According to the authors, the method could improve interpretation of phylogenetic results for a range of organisms.

http://www.pnas.org/content/early/2016/02/19/1522930113