A unique strain of hepatitis B virus (HBV) found in the preserved organs of a mummified Korean boy sheds new light on the virus’s evolution and its spread across Asia, according to a study published in Hepatology and reported by ScienceDaily.

Israeli and South Korean researchers reconstructed the entire genetic structure of the virus from a liver biopsy of the child, who is believed to have lived during the 16th century. The virus belongs to genotype C2, a strain most commonly found in Southeast Asia.

In comparing the reconstructed virus’s genetic code to that of its modern counterpart, the scientists found significant differences. They attribute these changes to random mutations and to evolutionary selection brought about by such environmental pressures as patients’ immune responses and anti-hepatitis drugs. Based on the estimated rate of mutation, the study suggests that the mummy’s viral strain and the modern genotype C2 diverged somewhere between 3,000 and 1,000,000 years ago.

Researchers hope that further study of the ancient virus will provide useful insight into the spread and evolution of chronic hepatitis B.

According to the World Health Organization, there are over 400 million hepatitis B carriers worldwide. HBV is most prevalent in Africa, China and South Korea, where an estimated 15 percent of the population carry the virus.