These HIV-2 strains are probably dead-end infections, and each of them is most closely related to SIVsmm strains from sooty mangabeys living in the same country where the human infection was found.
How the SIV virus would have transformed into HIV after infection of the hunter or bushmeat handler from the ape/monkey is still a matter of debate, although natural selection would favor any viruses capable of adjusting so that they could infect and reproduce in the T cells of a human host.
The YHS is being administered in Massachusetts public middle schools and both the YHS and YRBS are being administered in Massachusetts public high schools.
Together, the YHS and the YRBS cover a wide range of topics and the combination of data will allow for powerful state specific estimates.
Available below are the 20 YHS reports, Frequently Asked Questions, the combined YHS and YRBS reports for the 2007 - 2013 results, and the 2007 - 2015 YHS questionnaires for middle and high school.
AIDS is caused by a human immunodeficiency virus (HIV), which was originated in non-human primates in Central and West Africa.
Genetic recombination had earlier been thought to "seriously confound" such phylogenetic analysis, but later "work has suggested that recombination is not likely to systematically bias [results]", although recombination is "expected to increase variance".