Analysis of genomic data extracted from the mummified remains of a small child shows that hepatitis B virus (HBV) may have existed in humans for centuries. Results were published in PLoS Pathogens.
The mummified remains, buried in the Basilica of Saint Domenico Maggiore in Naples, Italy, and dating to the 16th century, had been previously analyzed. Results suggested that the child was infected with smallpox (variola virus), and—as the oldest evidence supporting the presence of smallpox in Medieval times—provided a critical time stamp for its origin. This previous scientific analysis, however, did not include DNA testing.
For this more recent analysis, researchers used advanced DNA sequencing techniques and found that the mummified child was actually infected with HBV, rather than smallpox. This misidentification may have been caused by the presence of a facial rash (Gianotti-Crosti syndrome) on the mummy. The rash, which can develop in children infected with HBV, may have been mistaken for smallpox.
“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,” explains Hendrik Poinar, evolutionary geneticist, McMaster Ancient DNA Centre, and principal investigator, Michael G. DeGroote Institute for Infectious Disease Research, Hamilton, Ontario, Canada.
Poinar and fellow researchers teased out small DNA fragments from skin and bone tissue samples, and were able to recover the complete genome sequence of this ancient strain of HBV. In doing so, they found that it has changed very little over the past 450 years, and that the evolution of HBV is complex. Although they found a close relationship between both the ancient and modern strains of HBV, they were not able to measure the rate of evolution over the 450-year gap between the two.
According to Poinar, the importance of studying ancient viruses is relevant to modern times. Some estimates hold that more than 350 million people have chronic HBV infection, and that approximately 33% of the population worldwide has been infected with HBV at some time in their lives.
“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,” concluded Poinar.