The Disease Network
http://www.bbc.com/earth/story/20151119-we-know-the-city-where-hiv-first-infected-a-human
One of the topics discussed thoroughly both in class and in the study of networks is the “six degrees of separation,” also known as the “small world phenomenon.” In this article, Colin Barras discusses the origins of HIV-1 in west central Africa. More specifically, scientists have pin pointed its origin in 1920 to the city of Kinshasa, currently the capital of the Democratic Republic of Congo.
This is where the “small world phenomenon” plays a role. Since the Belgian colony was just recently made a capital, it was seen as an opportunity to seek employment for many young men and, as a result, sex workers too. During this time, the capital was also one the most interconnected cities in Africa due to an extensive rail network used by hundreds of thousands annually. It took only 20 years for the virus to spread to cities 900 miles away.
The spread did not stop from there. It continued to spread as Haitians returned home after working in the Belgian colony. In the 1970s, the U.S. was affected. The spread of HIV is still carefully studied today, most recently seeing an outbreak in Indiana in 2015. One important take away is the similarities found amongst the spread of sexual diseases. University of Oxford researcher Nuno Faria exclaims, “There is no reason to believe that other subtypes would not have spread as quickly as subtype B, given similar ecological circumstances.” In other words, when studying the rate of spread, it is not the disease that is important but rather the network created by a globalized society.