More Evidence for Hepatitis A Virus with Animal Origins

The hepatitis A virus likely originated with small mammals, according to findings published in the Proceedings of the National Academy of Sciences. In September, MD Magazine reported that seals carry the closest known genetic relative of hepatitis A, called phopivirus.

Researchers from the Universities of North Carolina at Chapel Hill and Bonn, in Germany, studied almost 16,000 samples from more than 200 small mammal specimens to search for hepatitis A related viruses among small mammals. The samples were collected across the globe from bats, rodents, hedgehogs, and shrews. The researchers tested for structural, genomic, antigenic, and pathogenic properties similarities.

“Prior to this study, we had no understanding of the origins of hepatitis A virus, an ancient and common threat to health in many regions of the world,” study author Stanley M. Lemon, MD explained in a press release. “Now we know that it evolved among small mammals such as bats, and spread from them to humans in the distant past.”

The researchers learned that the small mammals likely of animal origin, just as Ebola and HIV likely are as well. Because of the similarities between the samples investigated and the traditional hepatitis A virus, among properties of genetics, protein structures, immune response, and patterns of infection, the researchers concluded that the virus comes from animals.

“The study enables new perspectives for risk assessments of emerging viruses by investigating functional, ecologic, and pathogenic patterns instead of phylogeny only,” said Jan Felix Drexler, MD, corresponding author. “It is possible that insect viruses infected insect eating small mammals millions of years ago and that these viruses then developed into the precursors of the hepatitis A virus.”

Drexler added that without the animal hosts for the virus, it would have died out a long time ago in human populations. He stressed, however, that humans would not be able to contract hepatitis A virus from these types of animals.

A vaccine for hepatitis A virus was developed in 1995 and has drastically reduced domestic cases of the virus. But in developing countries, where the vaccine is less prevalent, the vaccine is less restrained. The World Health Organization estimated that in countries where the hepatitis A virus is endemic, all children are infected with the disease before they turn nine years old.