Human Immunodeficiency Virus Type 1 (HIV-1) Subtype B Epidemic in Panama Is Mainly Driven by Dissemination of Country-Specific Clades

The Human immunodeficiency virus type-1 (HIV-1) subtype B is the most predominant clade in Central America; but information about the evolutionary history of this virus in this geographic region is scarce. In this study, we reconstructed the spatiotemporal and population dynamics of the HIV-1 subtype B epidemic in Panama. A total of 761 HIV-1 subtype B pol sequences obtained in Panama between 2004 and 2013 were combined with subtype B pol sequences from the Americas and Europe. Maximum Likelihood phylogenetic analyses revealed that HIV-1 subtype B infections in Panama derived from the dissemination of multiple founder viruses. Most Panamanian subtype B viruses (94.5%) belong to the pandemic viral strain proposed as originated in the US, whereas others (5.5%) were intermixed among non-pandemic Caribbean strains. The bulk (76.6%) of subtype B sequences from Panama grouped within 12 country-specific clades that were not detected in other Central American countries. Bayesian coalescent-based analyses suggest that most Panamanian clades probably originated between the early 1970s and the early 1980s. The root location of major Panamanian clades was traced to the most densely populated districts of Panama province. Major Panamanian clades appear to have experienced one or two periods of exponential growth of variable duration between the 1970s and the 2000s, with median growth rates from 0.2 to 0.4 year(-1). Thus, the HIV-1 subtype B epidemic in Panama is driven by the expansion of local viral strains that were introduced from the Caribbean and other American countries at an early stage of the AIDS pandemic.