By Liz Highleyman

HIV originally came to the U.S. from Haiti as early as the late 1960s, according to an analysis published in the October 31, 2007 advance online edition of Proceedings of the National Academy of Sciences - USA.

The HIV/AIDS epidemic was identified among American gay men in 1981, but researchers believe the virus was present but unrecognized well before this point. In the early years of the epidemic, Haitians were identified as one of the main risk groups.

HIV-1 group M subtype B was the first type of HIV discovered, the study authors wrote as background. It remains the predominant type outside of sub-Saharan Africa, including the U.S., Europe, and Australia. It is thought that HIV may have first infected humans in central Africa in the 1930s.

The researchers analyzed HIV-1 gene sequences from stored blood samples from 5 of the earliest known AIDS patients seen in 1982 and 1983, and compared the sequences to those from more than 100 individuals with HIV around the world. Viral diversity is greatest in areas where a virus has been present for a longer period, since it has had more time to evolve and develop mutations.

Analysis of viral "family trees" showed that subtype B HIV-1 likely moved from central Africa to Haiti between 1962 and 1970 (probably around 1966) and spread in the island nation for some time. Many Haitians worked in the Democratic Republic of Congo in central Africa after the country gained independence in 1960.

This viral strain likely moved from Haiti to the U.S. around 1969 (range 1966 to 1972), probably carried by a single person who came to a large city such as New York or Miami. The genetic analysis showed that HIV in the U.S. probably did not come directly from Africa. While many HIV positive people may have come to the U.S. from Haiti during these years, only one viral variant managed to spread widely.

"[E]ven if there is some uncertainty regarding precisely when HIV-1 entered Haiti or the United States, there is little doubt about the sequence of events," the authors wrote. "[T]he clear-cut topological information implies that the entry to Haiti occurred first."

From the initial case, the pandemic viral variant then spread throughout the U.S. for about 12 years before AIDS was recognized, as well as to Western Europe and elsewhere around the world. The analysis also suggests that a different strain of HIV-1 from Haiti sparked the AIDS epidemic in the Caribbean.

"Our findings imply that Haiti has the oldest-known HIV/AIDS epidemic outside of sub-Saharan Africa, which helps explain the high prevalence of AIDS and HIV-1 among Haitians in the early 1980s," the authors concluded. "Because of its 40-year history, the HIV-1 epidemic in Haiti exhibits a greater range of viral genetic diversity than the rest of the world's subtype B strains combined, much as the HIV-1 epidemic in the Democratic Republic of the Congo does for group M as a whole."

Viral diversity presents a challenge for vaccine development, since an effective preventive vaccine would need to work against all strains present in a given area.

Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ; Centre for Ancient Genetics, Niels Bohr Institute and Biological Institute, University of Copenhagen, Denmark; Institute for Evolutionary Biology, University of Edinburgh, U.K.; National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, GA; Department of Medicine, University of Miami, FL.

11/06/07

Reference
MTP Gilbert, A Rambaut, G Wlasiuk, and others. The emergence of HIV/AIDS in the Americas and beyond. Proceedings of the National Academy of Sciences - USA. October 31, 2007 [Epub ahead of print].