Hepatitis A is a highly contagious liver infection caused by the hepatitis A virus. It is usually transmitted by the fecal-oral route, either through person-to-person contact or through consumption of food or water. Hepatitis A viral infection impacts 1.4 million people worldwide annually. Until now, scientists thought that hepatitis A had no close relative and only human beings and other primates could be infected by such viruses. However, now they have identified a deadly strain of a new virus in seals which is the closest-known relative of the human hepatitis A virus. The discovery provides new clues on how hepatitis A could have emerged on earth.
Simon Anthony, assistant professor of epidemiology from Columbia University's Mailman School of Public Health, said, "Our findings show that these so-called 'hepatoviruses' are not, in fact, restricted to primates and suggest that many more may also exist in other wildlife species. Our data suggest that hepatitis A and this new virus share a common ancestor, which means that a spillover event must have occurred at some point in the past."
These findings raise the question of whether hepatitis A originated in animals, like many other viruses that are now adapted to humans. The research team discovered the new virus while investigating a deadly strain of avian influenza that killed over 150 harbor seals off the coast of New England in 2011. They observed that this new virus was genetically similar to hepatitis A and named it phopivirus.
Further analysis of additional animals living off the coast of New England identified phopivirus in seven more animals. In the natural history of phopivirus and hepatitis A, it is unclear whether a common ancestor (virus) spilled over from human beings to seals, vice versa, or from a third unrelated host that has not yet been identified. However various factors, including the fact that the phopivirus was found in different species of seals, suggest that the virus has been present in seals for a fairly long time.
The researchers now plan to look at species that have close interactions with seals to see if they can find other wildlife reservoirs of hepatitis A-like viruses.
The research appears in mBio