This brief introduction to HIV phylogenetics is the first of three briefs on the phylogenetics of HIV. This brief introduces phylogenetics, explains how the genetic code can be read, and shows how the sequences can reveal insights into HIV biology and epidemiology. The second brief explores what we have learned from HIV phylogenetic studies and how HIV phylogenetics can and should be used to support public health programmes. The third brief discusses the ethical considerations of HIV phylogenetics, including the need for appropriate care and safeguards of sensitive information.

References and full report details as well as partner-specific recommendations are available in the main report.