Using advanced DNA sequencing on a 16th-century mummy, a team of scientists has revealed the complex history and evolutionary processes of Hepatitis B (HBV). This genomic data is the oldest evidence of the virus and suggests that humans have lived with – and perhaps evolved alongside – HBV for centuries.
The study, published in PLOS Pathogens, notes that there has been "considerable uncertainty over the time-scale of [HBV's] origin and evolution." However, recent genomic data extracted from the 450-year-old mummified remains of a child buried in the Basilica of Saint Domenico Maggiore in Naples, Italy, has added more to the story.
Previous analysis did not use DNA testing and identified the child as having been infected instead with the Variola virus, or smallpox. It was believed to be the earliest dated evidence of smallpox.
Children infected with HBV can develop a facial rash known as Gianotti-Crosti syndrome, similar to the same blistering rash from smallpox. It is a possible misidentification that illustrates the challenges of identifying infectious diseases in the past.
Using advanced DNA sequencing techniques, scientists used small tissue samples of skin and bones to tease out tiny fragments of DNA, then stitched together bits of genetic information to recreate an HBV genome.
"These data emphasize the importance of molecular approaches to help identify the presence of key pathogens in the past, enabling us to better constrain the time they may have infected humans," said Hendrik Poinar, evolutionary geneticist and infectious disease researcher, in a statement.
Viruses can evolve rapidly – sometimes in just a matter of days – but researchers suggest this ancient strain of HBV has changed little over the last 450 years. That's because both the ancient and modern strains of HBV are missing temporal structure, which is a measurable rate of evolution throughout the period that separates the mummy and modern examples.
If genuine, this phylogenetic pattern indicates that the genotypes of HBV diversified long before the 16th century and enables comparison of potential pathogenic similarities between modern and ancient HBV.
"The more we understand about the behavior of past pandemics and outbreaks, the greater our understanding of how modern pathogens might work and spread, and this information will ultimately help in their control," said Poinar.
HBV is a pervasive, complex, and deadly pathogen that attacks the liver, causing both acute and chronic disease. It is transmitted through contact with blood or other body fluids of an infected person. An estimated 257 million people live with the virus, with an estimated 887,000 deaths in 2015, mostly from complications.