IT WASN’T SMALLPOX, DNA ANALYSIS CLAIMS

RESEARCHERS INSIST 16TH-CENTURY MUMMIFIED CHILD DIED OF HEPATITIS B

Thirty years ago, Italian scientists announced they had found what appeared to be the oldest evidence of smallpox in a 16thcentury mummified child. Except, it wasn’t. A new analysis led by Canadian researchers found the child was actually infected with hepatitis B, not smallpox — making it the oldest isolation of hepatitis from any mummy or fossilized human remains. And the ancient strain appears to have barely changed over the past 450 years.

While one historic discovery has been debunked, the new study provides a critical time stamp for the origin of a disease that is carried by 350 million people globally, and kills almost one million each year.

Exactly when it entered human populations was unclear.

“Given its global prevalence and the presence of related viruses in other mammals including non-human primates, it is commonly believed that the virus has existed in human populations for many thousands of years,” the team wrote in PLOS Pathogens.

One of the best ways to understand a virus is to understand how it has evolved, said evolutionary geneticist Hendrik Poinar, of McMaster University’s Ancient DNA Centre. (Poinar was part of an international team that two years ago sequenced the genome of two woolly mammoths. He’s also the son of George Poinar, the paleobiologist whose work inspired the movie Jurassic Park.)

“Understanding the evolution and trajectory of infectious diseases is critical for its elimination and eradication,” Poinar said.

The new analysis is based on tiny fragments of DNA teased out of small skin and bone samples extracted from the mummified remains of an anonymous child buried in the Basilica of Saint Domenico Maggiore, one of the oldest churches in Naples, Italy.

The Sacristy of San Domenico Maggiore housed 38 wooden coffins or “arks” with the bodies of royal Aragonese and other Neapolitan nobles.

The two-year-old child mummy was exhumed between 1983 and 1985. Records indicate the mummy was left undisturbed from 1594.

Scientists initially thought the toddler had been infected with smallpox because of deep, pockmark scarring on the scalp, face, arms, palms of the hands and legs. Electron microscopic images also showed egg-shaped, virus-like particles that looked like Variola virus, or smallpox, suggesting the child died of a severe form of the disease some four centuries ago, University of Pisa researchers reported in The Lancet in 1986.

“It was an interesting paper at the time, and it certainly was of landmark,” Poinar said.

But the earlier analysis didn’t include DNA testing.

Last year, Poinar and his team at McMaster published a paper on a 17th century Lithuanian child mummy that had smallpox. Afterwards, he and his team decided to analyze the Italian mummy to explore the diversity of smallpox within Europe.

“We tried everything in our power to find smallpox in this mummy,” Poinar said. “We could not for the life of us find any.”

The easiest explanation was that the DNA had deteriorated — but that wasn’t the case.

“We had this very strange case of perfectly well preserved DNA but no indication of smallpox, yet features on the face and the trunk and arm and the electron microscopy all saying this was a pox-like virus in this child,” Poinar said.

Using advanced sequencing techniques the mummy kept coming back “smallpox absent” but “hepatitis positive.”

Then, buried in old research, they found a syndrome called GianottiCrosti, where children with severe HBV infections develop a rash on the face and trunk.

“This is a clear case of HBV infection mimicking smallpox,” Poinar said.

Viruses often evolve rapidly, but when they analyzed the ancient hep B strain, they found a close relationship with modern ones. It looked like a strain from the 1980s.

The researchers had a moment of panic: maybe the hep B didn’t come from the child mummy. Maybe the excavators infected it?

“Probably statistically more likely is that HBV just does not have a clocklike rate of evolution,” Poinar said.

GINO FORNACIARI / UNIVERSITY OF PISA Pictured are the mummified remains of a small child buried in the Basilica of Saint Domenico Maggiore in Naples, Italy. An earlier analysis suggested the child had died of smallpox because of scars on its face.

Hendrik Poinar