HIV-2 infection is predominantly found in West African nations, such as Guinea-Bissau, The Gambia, Senegal, Cape Verde, Cote d'Ivoire, Mali, Sierra Leone, and Nigeria. In the late 1980s, each of these countries had a reported prevalence of >1% of the national population [1
]. An estimated 1 to 2 million people in West Africa are infected with HIV-2 [2
]. However, in recent years, HIV-2 prevalence has been declining in several West African countries, particularly among younger people [3
]. For example, in a rural area of northwestern Guinea-Bissau, the HIV-2 prevalence dropped from 8.3% in 1990 to 4.7% in 2000; during the same period HIV-1 prevalence increased from 0.5% to 3.6% [5
]. These trends may be related to the lower transmission efficiency of HIV-2 compared with HIV-1.
HIV-2 infection has also been reported in countries with historical and socio-economic ties to West Africa. For example, HIV-2 may have spread from Guinea-Bissau to Portugal during the war of independence [6
]. HIV-2 has also been reported in former Portuguese colonies, such as Angola, Mozambique, and Brazil, and in parts of India with previous ties to Portugal, such as Goa and Maharashtra. In Portugal, HIV-2 is responsible for 4.5% of AIDS cases] [7
]. In France, of 10,184 new HIV diagnoses between 2003 and 2006, 1.8% were infected by HIV-2 (1.6% HIV-2 monoinfection and 0.2% probable HIV-1/2 dual infections) [9
In the United States, the first case of HIV-2 infection was diagnosed in 1987 in a West African woman who presented with central nervous system toxoplasmosis [10
]. Although the total number of known cases of HIV-2 in the U.S. is small, in New York City alone there have been 62 confirmed or probable cases of HIV-2 infection diagnosed and reported since the implementation of named HIV reporting in 2000 [8
]. Moreover, given the large number of immigrants from HIV-2 endemic areas living in the U.S., it is clear that the current number of cases is higher than older estimates [1
]. According to the 2000 U.S. Census, of the estimated 31.1 million immigrants, more than a quarter of a million people are from Western African countries with a high prevalence of HIV-2 infection [11
]. Although immigrants from West Africa are located throughout the country, there are areas of concentrated residence for specific groups. For example, of the estimated 200,000 Cape Verdeans in the United States, many have settled in New England states, such as Massachusetts and Rhode Island [12
]. In addition, large numbers of Nigerians and Sierra Leoneans have settled in East Coast states, particularly the Washington DC area [13
]. The Chicago area is home to a substantial number of Ghanaians [14
]. Therefore, health care professionals practicing in the United States should have a high index of suspicion for HIV-2 infection in immigrants from high-risk areas and their sexual partners, and a low threshold for HIV-2 testing in such individuals.