Cutting-edge genetic technology has shown how viruses were brought over to the Americas by European colonizers during the transatlantic slave trade, bringing further death and devastation to the continent.
It’s well-known that the European colonization of the Americas and the Columbian exchange brought over much more than new food, new technology, and new ideas. In the centuries following the Europeans’ arrival, Indigenous Americans suffered a dramatic population decline. A huge cause of this was the introduction of new pathogens that the native population had no immunity to – by some estimates, diseases killed up to 90 percent of the Indigenous population following colonization. Smallpox, for one, is thought to have been particularly ruinous.
However, direct evidence for the presence of specific viruses during this time is surprisingly sparse; we can make good guesses about disease outbreaks from historical accounts and other evidence, but many of the viruses themselves have escaped modern scientists. To fill in these glaring gaps, scientists extracted ancient viral DNA from the teeth of people buried during the Colonial Era at a chapel and the San José de los Naturales Royal Hospital in present-day Mexico City. This included Indigenous people and those of African descent. Their findings were published in the journal eLife.
This approach allowed the team to reconstruct three ancient human parvovirus B19 genomes and one ancient human hepatitis B virus genome from four different people. Both blood-borne human pathogens that are now found around the globe, parvovirus B19 most commonly causes fifth disease – a mild rash illness that usually affects children – while hepatitis B is a potentially life-threatening liver infection.
By comparing these genomes to the others from across the world, they found that the viruses likely originated in West Africa and were transferred across the Atlantic Ocean to the Americas where they settled into the local population. It also affirms the widely speculated view that multiple novel viruses hit America at the same time, which helps to explain why the disease outbreaks were so prevalent and devastating.
“Our results suggest that the viruses were introduced to the Americas by colonists engaged in the slave trade,” co-senior author Daniel Blanco-Melo, co-senior author of the study and former postdoctoral researcher at the Icahn School of Medicine at Mount Sinai in New York who is now an Assistant Professor at the Fred Hutchinson Cancer Research Center in Seattle, said in a statement.
“The cruel, unsanitary and overcrowded conditions on the ships that transported millions of people across the Atlantic was a favourable setting for the spread of infectious diseases. Therefore, this gruesome practice likely introduced new pathogens to Indigenous people who had no immunity to them,” added Blanco-Melo.
Another previous study looked at three skeletons buried in the 16th century CE near the San José de los Naturales Royal Hospital of Mexico City. They found that all three individuals were male with a Y-chromosome lineage that’s commonly found in people of Western or Southern African descent, indicating they were most likely forcibly taken to America as part of the transatlantic slave trade. Further genetic analysis, isotopic techniques revealed the unimaginably cruel and harsh lives that were endured by these people.