About Zoonotic Diseases
Zoonotic diseases—those that jump from animals to humans—are not uncommon phenomena, with increasing genetic evidence suggesting that even measles, smallpox, and diphtheria may be a result of cross-species infection. Salmonellosis, a bacterial infection that can progress to an AIDS-defining condition, is a prime example, most often the result of ingesting contaminated meat, eggs, or dairy products.
According to the natural transfer theory (also known as the bushmeat theory), a number of blood-borne zoonotic diseases are believed to have been passed to humans when a hunter or bushmeat vendor is bitten or cut with hunting or butcher the meat of a simian like the red-capped mangabey. (Even today, the mangabey and other monkey species are hunted for food.)
Prior to World War II, many sub-Saharan Africans were forced to turn to bushmeat as European colonists and traders stripped them of many of their traditional domesticated meat sources. The practice of eating to bushmeat over the period of decades likely provide SIV the opportunity to mutate and thrive in its human host as a new view virus, HIV.
Genetic Sequencing Confirms Geographical Origin
In order to determine this, the scientists compared the genetic diversity of viruses found in the Congo Basin, including the DRC and Cameroon. What they were able to determine was that, using the genetic clues and historical data, the outbreak did not start in Cameroon as previously thought, but was a result of the spread of the virus between Kinshasa and Cameroon as a result of river trade.
The investigators ultimately confirmed that the virus found in Kinshasa exhibited more HIV-1 genetic diversity than anywhere else—resulting from the spread of the rapidly mutating virus from person to person—as well as the oldest known HIV-1 genetic sequences.
From the 1920s to the 1950s, rapid urbanization and the development of railways made Kinshasa a transport capital, thereby allowing the spread of HIV-1 throughout the country and soon after to East and Southern Africa. The genetic footprint left during this period illustrated dissemination of the virus throughout the DRC (a country roughly the size of Western Europe) as people traveled on railways and along waterways to the cities of Mbuji-Mayi and Lubumbashi in the south and Kisangani in the north.
Between the 1950s and 1960s, the use of unsterilized hypodermic needles in sexually transmissible diseases clinics and the growth of commercial sex trade were among the factors for the rapid spread of the viruses, particularly in mining communities where there was (and continues to be) a high migratory workforce.
During the 20-year period, the transport systems that enable the virus’ spread were less active, but it scarcely mattered. By the start of the 1970s, the seeds of the pandemic were already well sown and fast making their way toward North America and Europe thanks to increased air and ocean travel.
It was not until 1981 that the first cases of AIDS were identified in the U.S., followed by the isolation of HIV-1 virus in 1983. Today, as a result of the global pandemic, over 75 million infections have occurred, resulting in over 30 million deaths. As of 2018, the Joint United Nations Programme on HIV/AIDS reports that over 38 million people are known to be living with the disease worldwide.
