And then there is the threat of what have been dubbed "xenozoonoses," animal viruses that might be dangerous to people.
The plant picornaviruses have a number of properties that are distinct from the animal viruses.
It is also possible that an animal virus "jumped" into humans.
Now we have a very powerful animal virus circulating in Asia that is already moving into humans.
The chances that an animal virus will jump the species barrier are greater in places with constant contact between humans and animals.
This is the only animal virus within the order Mononegavirales to do this.
Growing animal viruses outside of the living host animal is more difficult.
Starting in the late 1940s, Hirst carried out pioneering research into the genetics of animal viruses.
Scientists at the lab study foreign animal viruses, including foot-and-mouth disease.
This is a feature of many bacterial and some animal viruses.