Until now, scarlet fever was considered one of the infectious diseases that were introduced to the New World by Europeans. But that’s not true, as DNA analyzes of a Bolivian mummy from pre-Columbian times have shown. The researchers discovered DNA from the scarlet fever pathogen Streptococcus pyogenes in the genome of the approximately 800-year-old mummy. Accordingly, these bacteria existed in the New World before Columbus. At least in this case, the conquistadors were not the bringers of the plague.
When the Spanish conquered the New World, it meant death for millions of indigenous people. The conquistadors not only raged with the sword, they also brought infectious diseases from Europe – including smallpox, measles, salmonella and the flu. Because the immune system of the indigenous population was not equipped to combat these foreign bacteria and viruses, these diseases were often fatal for those affected. The bacterial pathogen that causes scarlet fever and tonsillitis, Streptococcus pyogenes, was previously suspected of having been introduced to America by Europeans.
Genetic search for traces in an Andean mummy
However, a study has now shown that the scarlet fever pathogen was present in the New World before Columbus. A team led by Guido Valverde from Eurac Research in Bolzano discovered this while examining a mummy from the pre-Columbian period found in the highlands of Bolivia. According to dating, the dead man, a young man of indigenous descent, was buried in one of the typical burial towers of the Andean highlands between 1283 and 1383 AD. Both the Incas and some of their predecessor cultures used such chullpas for high-ranking deceased people, including grave goods. The cold, dry climate of the Andean highlands mummified and thereby preserved many of these dead.
To learn more about the body now kept at the National Museum in La Paz, Valverde and his team subjected dental samples from this natural mummy to DNA analysis. The so-called de novo assembly allowed them to assemble even highly fragmented, old genomes without the need for a reference genome. “You can imagine it like a puzzle that you put together without knowing the picture on the box,” explains co-first author Mohamed Sarhan from Eurac Research. This technique makes it possible to identify not only the deceased’s genetic material but also genetic traces of the pathogens that were once present in their tissues.
Streptococcus pyogenes was around long before Columbus
The researchers actually found what they were looking for: in the mummy’s genome samples, they identified numerous DNA sequences of the bacterium Streptococcus pyogenes – the causative agent of scarlet fever and tonsillitis. “The good state of preservation of DNA has allowed us to reconstruct an almost complete genome, which gives us a lot of information,” explains Valverde. “It shows, for example, that the bacterium could already cause diseases: the ancient strain had many, although not all, of the disease-causing genes of modern Streptococcus pyogenes strains.”
The presence of this pathogen in a corpse from the pre-Columbian period refutes the assumption that Streptococcus pyogenes also only came to the New World with the Europeans. Instead, the bacteria identified in the Bolivian mummy belonged to a very original strain of this pathogen that no longer occurs today. It split off from the remaining lineages of these bacteria around 10,000 years ago, as the team determined in comparative analyses.
However, it is still unclear whether the first human settlers of America brought this pathogen with them when they migrated from Siberia across the Bering Strait to North America. It is also conceivable that the bacterium circulated among animals in America and then spread to humans there. “The family tree position of this ancient Bolivian pathogen strain and the reconstruction of the last common ancestor would be consistent with an American origin of this pathogen,” write Valverde and his colleagues. “However, these observations are not sufficient to support such an interpretation.”
Overall, the results demonstrate that analyzes of ancient DNA can also reveal new insights into diseases in earlier cultures and their pathogens.
Source: Eurac Research; Specialist article: Nature Communications, doi: 10.1038/s41467-026-71603-9