Extremely rapid spread of human immunodeficiency virus type 1 BF recombinants in Argentina

Abstract

The epidemic of human immunodeficiency virus type 1 (HIV-1) in Argentina is distinctive in that many infections are caused by subtype BF recombinant viruses. To determine their demographic history, we estimated the evolutionary rate, mode of population growth, and age of genetic diversity among 40 BF vpu sequences. This revealed one of the highest substitution rates reported for HIV-1, at 10.793 x 10(-3) substitutions per site per year, and a very rapid rate of population growth, with an initial mean epidemic doubling time of 3.72 months. This rapid population growth is compatible with an elevated fitness for subtype BF compared to that for "pure" B and F viruses.

FIG. 1.

Maximum a posteriori phylogenetic tree of 40 CRF12_BF sequences from Argentina comprising the vpu gene and the 5′ end of the env gene. The precise day of sampling is given in the sequence identifier of each viral isolate. For isolate DIARG71/Jun2003, the exact day of sampling was unavailable so the mid-month date of 15 June was chosen to minimize error. In all cases, tip times correspond to the dates of virus sampling.

FIG. 2.

Incidence of MTCT in Argentina from 1986 to 2004. Incidence is expressed as the number of new HIV-1-infected newborns/10,000 children born alive. The source was the National AIDS Bulletin of Argentina (2005) (10). The data for 2004 (open circle) are preliminary.