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How Colonial Congo's Diamond Trade Helped Turn HIV into a Pandemic

More trade led to more travel and a further spread to the disease.
Image: Carl Gierstorfer/Science

For the first time, scientists have used genetic data to track the early spread of HIV and its development into a global pandemic. The findings suggest that the infrastructure built by Belgian colonizers—notably railways that supported the diamond and gold trade—took what was a localized disease and turned it into a worldwide problem.

Oxford University's Nuno Faria suggests in a paper published today in Science that modern HIV can be traced back to the Congolese city of Kinshasa, where people there began being infected with the virus in the early 1920s.

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By using some of the earliest-available samples of the virus, combined with newer strains, Faria's team was able to study mutations in the virus and its diversity in populations to trace it back to Kinshasa.

the virus traveled with people along railways and waterways

Today's samples of HIV from people infected in Kinshasa show that the virus is most genetically diverse there, suggesting that the virus has had the longest time to evolve mutations. The finding "clarifies why the oldest known HIV-1 sequences were sourced from this city and why several early cases indicative of AIDS are linked to Kinshasa," according to the paper.

So Kinshasa is where it started. As the study notes, the disease was almost certainly passed from a monkey to a human, which has been observed at least 13 times in history. But only this one time, in Kinshasa, did it turn into a global epidemic.

Faria suggests in the paper that Belgian colonialism, infrastructure, and trade is the most likely culprit.

Congo was under Belgian rule between 1908 and 1960—during that time, the Belgians built a robust rail system and heavily expanded diamond and gold mining. Kinshasa was the center of that trade, and Faria suggests that those infected with HIV traveled by rail to mining towns and other city centers where they were able to pass on the disease.

"Data from colonial archives tells us that by the end of 1940s over one million people were traveling through Kinshasa on the railways each year," he said in a statement. "Our genetic data tells us that HIV very quickly spread across [the country], traveling with people along railways and waterways to reach Mbuji-Mayi and Lubumbashi in the extreme South and Kisangani in the far North by the end of the 1930s and early 1950s."

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In fact, that's about the only time this could have possibly occurred: After Congo secured its independence, railways in Congo became used much less often. Oliver Pybus, a researcher on the study, suggested that there was only a "small window" in which HIV could have emerged out of the city in enough numbers to cause pandemic.

In the late 1950s, changing sexual habits and public health initiatives (also implemented by the Belgians) that emphasized vaccination and treatment for other disease—campaigns that often reused needles—helped turn the outbreak into a full-blown pandemic.

The disease exploded in "high-risk groups of small size—for example, commercial sex workers with higher rates of partner exchange and/or exposure to contaminated injections."

From there, it spread into the general population. The team wrote that this explanation "agrees with available public health data and the hypothesis that transmission rates of [HIV] increased as a result of the administration of unsterilized injections at sexually transmitted disease clinics in the 1950s and/or subsequent changes in the nature of commercial sex work in Kinshasa from the early 1960s, which led to increased client numbers."

The team says that it's important to trace HIV back to its origins because it's "critical to our understanding of the establishment and evolution of human pathogens."