An international team of researchers discovered that the hepatitis A virus, previously thought to be a strictly human pathogen, is probably of animal origin. The research paper, entitled “The hepatitis A virus is of animal origin,” was published in PNAS.

Hepatitis A virus (HAV) infection can lead to severe liver inflammation, a situation that might resolve without symptoms or major complications in children but can lead to more serious symptoms and outcomes in adults. The origins of HAV are currently unknown. However, it is considered a human pathogen as only human cases — and a very few cases of non-human primates — have been reported.

To investigate the virus’ origins, virologists from the University of Bonn Hospital and researchers from other international institutes conducted a targeted search for viruses related to the HAV in small animals that had been globally sampled. A total 15,987 specimens from 209 different small animal species (rodents to shrews and bats to hedgehogs) were investigated. The scientists discovered that these viruses shared several similarities with the human HAV, in terms of structural, genomic, pathogenic, and elicited immune response properties.

These high similarities lead researchers to believe that the human HVA is most likely of animal origin. In addition, the scientists theorized that these results may also suggest the virus originates from precursor insect viruses and that small mammals were hosts for the preservation and evolution of HAV. This does not mean, however, that humans can contract HAV from animals, as explained by Prof. Dr. Jan Felix Drexler from the Institute of Virology at the University of Bonn Medical Centre and the German Centre for Infection Research: “Patients need not fear that they could contract a hepatitis A virus infection through bats or hedgehogs. It has likely been a very long time since humans first contracted the hepatitis A precursor virus from animals – moreover, such incidents are very rare.”

This study also represents a new and more broad approach to risk assessment of emerging viruses. “The study enables new perspectives for risk assessments of emerging viruses by investigating functional, ecologic and pathogenic patterns instead of phylogeny only,” Dr. Drexler concluded.