Human immunodeficiency virus I Escapes from Central Africa. 

     Humans fished and hunted in the Dzanga-Sangha Forest Reserve and along its rivers' banks for tens of thousands of years. About a hundred years ago, a hunter stalked, killed and butchered a chimpanzee that inhabited southern Cameroon along the mighty Sangha River. A bloodborne infectious virus from the chimpanzee and a hunter's skin cut began a chain of events which allowed this new micro-predator to escape from its home region. This microbe expanded slowly within the local population and, hidden within its human hosts, traveled southward along the Sangha River meeting the Congo River. Traveling southwest on the Congo River it made the journey to the regional capital Léopoldville (now Kinshasa, Democratic Republic of the Congo).  

     Using the sex trade as a conduit for infecting new hosts (and later reused needles and syringes), the virus successfully established a series of infections among a small group of carriers. It evolved into Human immunodeficiency virus-1 (HIV 1) and within a few decades began to expand exponentially. HIV would be dispersed by train and other methods across the region and world. By the late 1980s, the Acquired Immunodeficiency Syndrome (AIDS) disease, originating from HIV infection, would become one of the most feared globally infectious diseases ever known. Even with a decade long process required for the host to succumb to the infection and therapies to arrest the disease, by 2015 the HIV-1 pandemic spanned every continent and killed tens of millions of people. The travel history of HIV-1, rising from its humble origins to become one of the world’s most notorious emerging infectious diseases is how many parasites successfully established themselves as dominant predators on the earth. 

References: 

(1) Faria, Nuno R., et al. The early spread and epidemic ignition of HIV-1 in human populations. Science 2014; 346(6205): 56-61. https://commed.vcu.edu/IntroPH/Communicable_Disease/2015/HIVTravel_1900-nowFULL.pdf. 

(2) de Sousa JD, et al. Enhanced Heterosexual Transmission Hypothesis for the Origin of Pandemic HIV-1. Viruses 2012; 4: 1950–1983. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3497036/pdf/viruses-04-01950.pdf.

(3) Sharp, PM and Hahn BH. The evolution of HIV-1 and the origin of AIDS. Philos Trans R Soc London [Biol] 2010; 365(1550): 2487-2494. https://royalsocietypublishing.org/doi/pdf/10.1098/rstb.2010.0031.

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