Author(s): Yaxelis Mendoza 1,2,3,4,*, Gonzalo Bello 5, Juan Castillo Mewa 1, Alexander A. Martínez 1,2,4, Claudia González 1, Claudia García-Morales 6, Santiago Avila-Ríos 6, Gustavo Reyes-Terán 6, Juan M. Pascale 1
The Human Immunodeficiency Virus (HIV) is the causative agent of Acquired Immune Deficiency Syndrome (AIDS). During the past decade, the Panamanian HIV/AIDS epidemic has changed dramatically. The accumulated number of adults (15+ years) living with HIV increased from 5,000 to around 18,000-20,000 subjects between the years 2001-2010 , , whereas the number of newly infected people increased up to 14.9% (from 440 to 942 cases) in the same period , . At the beginning of the Panamanian epidemic, the majority of the infections had occurred between men who have sex with men (MSM); although, since 1991, there has been an increase in the number of infected women , . Nowadays, recent studies have suggested that the Panamanian epidemic does not have a predominant mode of sexual transmission because bisexual-homosexual and heterosexual modes have similar proportions . Finally, even though the total HIV prevalence has decreased from 1.4% to 0.8% in the general population since 2001 and the prevalence among female sex workers remains low (0.7-1.6%) , the prevalence among MSM continues to steadily increase and reached 23% in 2011 . A higher prevalence of HIV infections among MSM in the Americas was only observed in Jamaica (38%) .
The main characteristic of HIV infection is the high genetic variability of virus isolates obtained either sequentially from the same infected subject or from different subjects -. Phylogenetic studies allow the classification of HIV-1 isolates into four main groups (M, N, O and P) . Currently, HIV-1 group M is responsible for most HIV-1 infections worldwide and has been classified into nine subtypes (A-D, F-H, and J-K), 55 circulating recombinant forms (CRFs) and a large number of unique recombinant forms (URFs) , . HIV-1 subtype B is the predominant variant in the Americas; although non-B subtypes have also been described with high prevalence in Cuba, Brazil, Argentina, and Uruguay . Panamás geographical position and its historical mission as a country of transit since the colonial era have made the country a highly cosmopolitan nation with close historical and cultural links with Central, North and South America and the Caribbean. Therefore, the genetic diversity of HIV-1 in Panama is expected to resemble the diverse genetic profile observed in other parts of the Americas and the Caribbean. The only other HIV-1 molecular epidemiologic survey performed in Panama to date, analyzed the gag , pol , and env genes of 133 samples collected between 2004 and 2005, reporting a high prevalence of subtype B (97%) and only two cases of non-B-subtypes (one CRF12_BF and one CRF02_AG) , . The aim of our study was to expand our comprehension of the HIV-1 subtype distribution in Panama by the phylogenetic analysis of the pol region of a large number of individuals (n = 655) from different regions of the country that were diagnosed over a long time period...