Net migration rates over 5-year intervals.

Mean number of immigrating and emigrating people per 1000 individuals over different 5-year intervals from 1950 to 2010 for Guinea-Bissau and neighbouring countries (Guinea, Mali, Senegal, and The Gambia). The pink area highlights the time period of the estimated HIV-1 introductions into Guinea-Bissau. Data were obtained from the United Nations World Population Prospects (United Nations Population Division, 2010) [33].