Since the mysterious deaths of a husband and wife from the Medici family, a powerful Italian dynasty that ruled Florence and Tuscany almost continuously from 1434 to 1737, rumors have circulated about what led to the couple’s untimely demise. Now, scientists believe they have an answer: it wasn’t murder, but malaria.
In 1587, Grand Duke Francesco I de’ Medici and his wife, Bianca Cappello, died within hours of each other after days of agony.
At the time, logic dictated that malaria was the culprit because the couple had shown symptoms of the disease, including a telltale intermittent fever. But rumors of a murder immediately spread, pointing to Francesco’s younger brother and rival, Ferdinando, as the perpetrator.
Ferdinando was next in line to the throne, but risked being passed over in favor of Francesco’s illegitimate son, Antonio. Furthermore, Ferdinando had visited the Grand Duke and his wife at their residence just before they fell ill, further reinforcing the suspicion that he poisoned them with arsenic to ensure his own rise to power.
The couple fell ill in a Medici villa in Poggio a Caiano, near Florence, an area dotted with swamps and rice paddies, ideal habitats for mosquitoes that can transmit malaria. Still, rumors of murder persisted, likely fueled by the Medici family’s history of murders and attempted murders.
Since 2004, when the exhumation and analysis of skeletal remains from 49 Medici family tombs began as part of the Medici Project, various studies have confirmed malaria as the cause of Francesco’s death. However, other studies published as recently as 2006 used toxicological investigations to determine that the couple were, in fact, victims of arsenic poisoning.
A new study conducted jointly by the University of Pisa in Tuscany and Yale University used DNA extracted from the skeletal remains of Francesco and another of his brothers, Giovanni, in an attempt to settle the debate once and for all.
“In recent years, we tried to solve this mystery by carrying out some specific analyses, in particular paleo-immunological analyses, which attested to the presence of malaria in the remains. But the rumors did not stop, because paleo-immunology is not conclusive, and only ancient DNA could give an answer with a high degree of certainty,” said Valentina Giuffra, professor of history of medicine at the University of Pisa and co-author of the study, published in June in the journal iScience.
Paleo-immunology uses antigens, substances that trigger an immune response, or proteins to check for traces of disease in ancient remains. DNA analysis, which is a newer approach, is more definitive because it looks for direct genetic signatures of a disease.
Giuffra and his colleagues found genetic traces of plasmodium, the parasitic protozoa responsible for malaria, in samples of bone material from Francesco’s ribs. “The DNA is conclusive,” Giuffra said. “It solves the problem and the doubts. I think this is a definitive answer.”
Malaria is one of humanity’s great historical killers, causing 610,000 deaths in 2024 alone, according to the World Health Organization. It manifests itself with fever, headaches and chills, and its name comes from the medieval Italian phrase “mal aria,” meaning bad air, a nickname derived from the idea that the disease was contracted by breathing foul-smelling air near swamps or stagnant water.
Historical sources supported the assumption that malaria killed Francesco and Bianca, Giuffra said. Documents written by doctors at the Medici family court described symptoms compatible with the disease. They also detailed some treatments administered to patients, such as bleeding, the deliberate extraction of blood, which at that time was believed to free the patient from an illness, but which in reality worsened their condition.
The genetic analysis was performed on small bone samples set aside when the Medici tombs were opened in 2004, before the rest of the remains were reburied. Scientists couldn’t perform a similar analysis at the time because the technique wasn’t developed enough, Giuffra said.
The new study found not just one, but two species of the malaria parasite—Plasmodium falciparum and Plasmodium malariae—in Francesco’s remains, suggesting he may have been the victim of a double infection. Investigators also analyzed the remains of Cardinal Giovanni de’ Medici, Francesco’s younger brother, who, along with two other family members, died 25 years earlier after a trip to the Tuscan coast. Malaria was also found in Giovanni’s sample, in the form of a previously unknown strain of Plasmodium falciparum.
“Francesco and Giovanni, a young member of the family, both traveled 25 years apart to areas of Tuscany that were known for malaria,” Giuffra said.
“Court doctors tried to dissuade some members of the Medici family from making these trips, especially in autumn, which was a particularly favorable season for malaria. But they went anyway and, a few days after the trip, they began to develop the first symptoms, including an intermittent fever, which is associated with malaria infection.”
Detecting different species of malaria also helps track the evolution of the disease. “Our study contributes to filling a historical gap for a time, the Renaissance, and a space, central Italy, for which there is very limited information on the evolution and spread of malaria,” Alexander Ochoa, an associate research scientist at Yale and first author of the study, said in an email.
But is there any guarantee that Francesco was not also poisoned?
“Maybe not,” Ochoa said, “but the genetic evidence presented in our study reduces the room for speculation.”
Gisella Caccone, a senior research scientist also at Yale and co-author of the study, agrees. “We can say they had malaria, we can’t say they weren’t poisoned as well,” Caccone said in an email.
“It was already assumed at that time that they had malaria, due to the symptoms they had and the fact that they traveled to the malaria-infested swamps in southern Tuscany… if in addition to this someone decided to hasten their departure by poisoning them, we will never know. But how likely is it?”
Donatella Lippi, a professor of the history of medicine at the University of Florence and co-author of the 2006 study that supported the murder hypothesis, said she still believes Francesco was poisoned. “Getting malaria does not mean dying from it, and this research supports what I have always maintained,” Lippi, who was not involved in the study, wrote in an email.
In the case of Francesco’s death, he added, Vatican Library records mention skin rashes, fever and swelling, all symptoms of acute arsenic poisoning.
“I believe that Francesco I suffered from malaria, but he was poisoned and died from the poison. His tomb was opened 300 years after his death; his hands were contracted as if he were in the throes of agony, and the body was well preserved; arsenic could explain both.”
Giuffra noted that Lippi’s findings are not based on skeletal remains exhumed from Francesco’s grave, but on biological tissue found in a different location where some of Francesco’s organs were supposedly placed after an autopsy, according to historical records used by Lippi. Francesco was known to be an alchemist who experimented with chemicals, which could explain the skin rashes, Giuffra added.
The study is interesting, both from a historical perspective and from that of ancient pathogens, said Anne Stone, a Regents Professor in the School of Human Evolution and Social Change at Arizona State University. Stone, who was not involved in the work, suggests that the brothers died from a malaria infection, but that toxicological analyzes would need to be performed to see if the poison also played a role.
“Recovering pathogen DNA from centuries-old human remains is technically very difficult,” David Caramelli, a professor of anthropology at the University of Florence who was not involved in the study, said in an email.
“Although the study provides evidence consistent with malaria infection, I do not believe it definitively resolves the long-standing debate about malaria versus poisoning. The presence of pathogen DNA is not necessarily equivalent to proving the cause of death, and genetic evidence should always be interpreted in conjunction with historical, archaeological, and pathological data.”
Nevertheless, Caramelli concluded, the new research represents an important step forward and demonstrates how paleogenomics can help address long-standing historical questions.
