Pedro, Israel is not to blame: The Spanish brought the world's deadliest disease to America
Remains of smallpox virus DNA found in two mummies of indigenous people in northern Chile provide, for the first time, direct genetic evidence that the disease arrived in the Americas with European conquerors. Researchers identified an extinct viral lineage, dubbed CAM9.
Remains of smallpox virus DNA found in two mummies of indigenous people in northern Chile provide, for the first time, direct genetic evidence that the disease arrived in the Americas with European conquerors. Researchers identified an extinct viral lineage, dubbed CAM9, and determined that it originated from strains of the smallpox virus that circulated in Europe during the period before and during the Spanish conquest.
The study, published in the scientific journal Science, was based on a genetic analysis of the remains of two individuals buried at the Camarones site in northern Chile. According to the researchers, the findings reinforce the historical understanding that smallpox was among the diseases brought by Europeans that caused severe damage to indigenous populations in the Americas.
The researchers identified the virus in femur bone samples of a 30–35-year-old woman and an 18–20-year-old man. The remains were preserved inside bundles of South American camelid wool, and tests showed that both individuals were likely infected with the same viral strain or during the same outbreak wave between 1492 and 1631.
The virus, named CAM9, was found to be genetically close to medieval European strains and to a virus found in a 17th-century mummy in Lithuania. By building an evolutionary "family tree" of the virus, the researchers determined that the Chilean lineage belongs to a line originating in the Old World. According to the analyses, CAM9 separated from a European branch around the year 1296, a figure that fits historical evidence regarding the spread of the disease across the Atlantic Ocean during the period of the Spanish conquest.
Smallpox is caused by the variola virus and was for centuries one of the deadliest diseases for humans. Before the disease was declared eradicated globally in 1980, it had afflicted populations for at least 1,500–2,000 years, killing an estimated one-third of those infected and leaving many survivors with scars.
In the Americas, where indigenous populations had no prior exposure to the virus and therefore no natural immunity, the disease spread rapidly. According to historical estimates, it caused the deaths of between three and four million people on the continent, and in some areas, it may have killed up to 90% of the indigenous population.
Until today, there has been a debate among historians regarding the exact route by which the disease reached the Americas—whether through Spanish settlers, via slave trade routes from Africa, or through transmission between indigenous communities. The new genetic information points to a European origin of the strain found in Chile, but the researchers emphasize that it is still not possible to determine with certainty how exactly the virus reached the remote populations.
"The discovery of smallpox DNA in early colonial Chile is of immense importance," said Hendrik Poinar, a researcher of ancient genetics, after previous studies failed to locate direct evidence of the virus from this period. Poinar added that researchers are still "no closer to knowing what the true reservoir species is from which smallpox originated," meaning what animal or ancient source the virus existed in before it became a human disease.
