Today has seen a flood of press stories about a new study which strongly suggests that HIV-1 subtype B migrated into the US from Central Africa by way of Haiti. The stories were instigated by a press release from the University of Arizona, publicizing a paper by Michael Worobey and colleagues which is apparently due for online publication in PNAS later this week. Rather awkwardly, the paper does not seem to be online as yet (UPDATE 10/31: the PNAS article is now online, although to the journal's discredit they have not made it open access. UPDATE 11/1: I guess I wasn't the only person who thought the paper should be open access, to their credit PNAS has now made the PDF available free of charge). Anyone interested in finding out more details about the study can watch Michael Worobey's presentation at CROI earlier this year; just go to the webcast page and then scroll down to the session entitled "Oral Abstracts: Epidemiology: Transmission Dynamics and Risk." Click on "Play Video" and Worobey's presentation is the first in the session.
Sadly, the study is re-igniting controversies regarding Haitians somehow being blamed for HIV (as happened, with horrible consequences, in the early 1980s). You can hear an angry response to Worobey's presentation by a Haitian researcher at the end of the CROI webcast, and Jean Pape is quoted in an article in Science by Jon Cohen saying that the study authors "restate prejudices advanced 2 decades ago." However, it seems clear that the researcher's interest is in using molecular techniques to track the history of HIV's spread, not in judging any person, nation or ethnicity. Some press stories have highlighted the suggestion that one transmission event from Haiti around 1969 triggered the US epidemic, and made the leap that - if true - the individual in question must have been Haitian. But the study makes no such implication; only that the genetics of early HIV sequences provides strong evidence that the virus circulated in Haiti prior to the US and that a single transfer event occurred; if a single individual did transfer the virus between the countries, they could have been of any ethnicity and the transfer was almost certainly an inevitability. The study authors do suggest that it might have been an infected Haitian worker returning from the Congo that transferred HIV from Africa to Haiti around 1966 but this is speculation; the molecular data supports the hypothesis that the virus moved between those two places around that time but says nothing about how the transfer occurred. It is dismal to realize that the stigma associated with HIV because of how it is transmitted remains strong enough to severely complicate the discussion of this type of study in 2007.
Gilbert MTP, Rambaut A, Wlasiuk G, Spira TJ, Pitchenik AE & Worobey M
(2007) PNAS In press
HIV-1 group M subtype B was the first human immunodeficiency virus discovered and is the predominant variant of AIDS virus in most countries outside of sub-Saharan Africa. However, the circumstances of its origin and emergence remain unresolved. Here we propose a geographic sequence and timeline for the origin of subtype B and the emergence of pandemic HIV/AIDS out of Africa. Using HIV-1 gene sequences recovered from archival samples from some of the earliest known Haitian AIDS patients, we find that subtype B likely moved from Africa to Haiti in or around 1966 [1962-1970] then spread there for some years before successfully dispersing elsewhere. A ?pandemic? clade, encompassing the vast majority of non-Haitian subtype B infections in the US and elsewhere around the world, subsequently emerged after a single migration of the virus out of Haiti in or around 1969 [1966-1972]. Haiti appears to have the oldest HIV/AIDS epidemic outside sub-Saharan Africa and the most genetically diverse subtype B epidemic, which might present challenges for HIV-1 vaccine design and testing. The emergence of the pandemic variant of subtype B was an important turning point in the history of AIDS but its spread was likely driven by ecological rather than evolutionary factors. Our results suggest that HIV-1 circulated cryptically in the US for approximately twelve years before the recognition of AIDS in 1981.