When phylogenetic analysis complements the epidemiological investigation: a case of HIV-2 infection, Italy.

Human immunodeficiency virus type 2 (HIV-2) infection is geographically restricted, affecting West African countries such as Guinea- Bissau and Cape Verde. We describe a recent case of HIV-2 infection in an Italian patient. Phylogenetic analysis of the V3 region of HIV-2 indicated that the Italian patient was infected by HIV-2 subtype A2. The sequence obtained from the Italian patient clustered significantly with a sequence isolated from Senegal. A phylogenetic doubt may arise from a Guinea Bissau sequence because it was in a major clade with the Italian and Senegal sequences, but was not statistically significant. The discovery of another Italian case over a short time frame stresses the importance of strengthening the surveillance system for HIV-2 because of the increase in migration from endemic areas to Italy.