Hepatitis A Found in Seals: Can It Reach Humans?

Investigators question if hepatitis A virus originated in animals.

Seals carry a virus that is the closest known relative of the human hepatitis A, according to research published in the journal mBio.

Researchers from the Mailman School of Public Health at Columbia University originally were investigating a deadly strain of avian influenza that killed more than 150 harbor seals in New England in 2011. In their research, the team performed a deep sequence of all the viruses present in 3 of the seals to determine which viruses might co-occur with influenza.

The newly discovered virus named phopivirus was genetically similar to hepatitis A. After an additional screening of 29 harbor seals, 6 harp seals, and 2 grey seals, the study authors found phopivirus in 7 more animals. The virus appeared to be fairly common, according to the researchers, who extrapolated the data based on the findings of their original influenza study.

“Until now, we didn’t know that hepatitis A had any close relatives, and we thought that only humans and other primates could be infected by such viruses,” lead author Simon Anthony, PhD, assistant professor of Epidemiology, explained in a press release. “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.”

The investigators did not find evidence that phopivirus causes the animals any harm. The researchers did warn, however, that further research is needed specifically targeting mature seals — because hepatitis A only causes damage in adults, phopivirus may operate the same way.

Hepatitis A infection impacts an estimated 1.4 million people globally and is highly contagious. Typically, the virus is transmitted to each new case via the fecal/oral pathway through person to person contact or through consumption of food or water.

“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,” continued Anthony. “It raises the question of whether hepatitis A originated in animals, like many other viruses that are now adapted to humans.”

The researchers still are unclear about whether there is a common ancestor to the hepatitis A virus and the new phopivirus, or whether the virus transferred from humans to seals or vice versa. A third unrelated common ancestor has not been ruled out, either. The researchers have concluded, though, that the virus seemed to have been present in seals for a long time, as it was found in three separate species.

In the future, the researchers will examine animals with close relationships to seals, like coyotes, a natural predator for seals, to determine if they have the virus or something similar. Additionally, the researchers may examine humans who eat seal meat to see if the seal virus is present in humans or if it has manifested as hepatitis A.