Sixteenth-Century Child Diagnosed With Hepatitis B:
An international team of disease detectives has shed new light on a virus that kills nearly a million people worldwide every year by searching for an unusual source — the mummified remains of a young child who died in Renaissance Italy about 450 years ago.
The scientists were able to sequence the complete genome of an ancient strain of hepatitis B after extracting DNA from the naturally mummified body of the 2-year-old girl, which was interred with a number of other bodies in the sacristy of the Basilica of Saint Domenico Maggiore in Naples.
Before the advent of advanced genomic sequencing in the mid-1980s, Italian researchers suggested that the child was probably killed by smallpox due to evidence of rash scarring on her body.
“The blisters are clearly all over the face … when you look at the photo, your first thought would be smallpox,” agreed Hendrik Poinar, an evolutionary geneticist at McMaster University in Hamilton, who co-led the new study with evolutionary biologist Edward Holmes of the University of Sydney.
But after extracting viral DNA from small samples of the child’s skin and bone and analyzing its genetic signature, researchers turned up no proofs of smallpox.“Nada. We could not find anything,” said Poinar, director of McMaster’s Ancient DNA Centre, who previously helped sequence the genome of the extinct woolly mammoth and traced the genetic evolution of the bacteria that causes bubonic plague.
One of the scientists then turned to what’s called a pathogen enrichment array, a means of testing a DNA sample to see if there is a genetic match detected among markers for 100’s of viruses, bacteria, and other disease-causing agents.
What emerged was a clear signal for hepatitis B, leading the researchers to speculate that the child may have been affected by a rare childhood disease that can follow infection with hepatitis B, known as Gianotti-Crosti syndrome.“That’s a rash that breaks out extensively on children and it can cause death,” said Poinar.
What surprised the scientists, whose research was published in PLOS Pathogens on Thursday, was how little hepatitis B strain in the 16th century had changed genetically compared to modern – day virus samples.
Hepatitis B is a primarily blood-borne virus that affects the liver. While most adults recover fully from the disease within a few months as their immune system clears the infection, some people develop a chronic lifetime infection that can lead to cirrhosis or liver cancer. A vaccine can prevent hepatitis B, but there is no curative treatment.
It is estimated that 1/3 rd of the world’s population has been infected with the virus at some point in their lives and that about 350 million people are currently living with a chronic infection.
“This is a virus that still causes considerable morbidity and mortality today across the globe, especially in under developed countries and for lower socioeconomic status individuals,” said Poinar, noting it began infecting humans about 60,000 years ago.
“The more we understand the behavior of past pandemics and outbreaks, the more we understand how modern pathogens can work and spread, and this information will ultimately help them to control them,” he said. “Understanding the evolution of pathogens is essential to understanding how to eradicate them.”