Expert: John Locke - 12/9/2007

Question
If someone carrying a virus(for example, Anthrax) died, and a carnivore were to
eat the body, could the virus become a danger again?

Answer
Thanks for using AllExperts, Alec. There's no simple answer to this question because not all viruses are alike. Let's start at the beginning with the dead body of the animal that's going to be eaten. Viruses might not even survive the death: some are relatively fragile and die when the host (that's the person or animal carrying the disease) dies. Others are more robust and can survive for some time in the blood and body tissue after the host dies--if another host comes along and contacts that blood or body tissue, that person can become infected in turn. HIV, for example, will survive in blood and body tissue for some time after a person carrying the disease has died; eventually, the tissue will break down, resulting in the death of the viruses within the tissue. And some viruses are extremely durable because of their ability to form crystal- or spore-like structures (anthrax can do this, notably). These crystals can persist in the environment for years without breaking down.

Some viruses also don't cross between species: plant viruses can't infect humans, even those who eat plants infected with those viruses. The smallpox virus is able to live only in humans, which was the primary reason doctors were able to eliminate it from the earth (the virus simply couldn't live anywhere else). Compare this to anthrax, the Ebola virus, or Heptatitis B, all of which can pass between species. Obviously, if a carnivore were to eat the flesh of animal that had a virus it could not catch, then the risk would be non-existent.

Now let's consider a carnivore eating the body of an infected animal, where the carnivore could be affected by that virus; assume for a second that the virus in question has survived the death of the host and is still residing in the tissue. The carnivore that comes along and eats the host's body may or may not become infected--again, because some viruses are more robust than others, and because different viruses infect different parts of the body. A respiratory virus like influenza probably wouldn't pose a risk to a carnivore eating a carcass infected with it, because influenza is spread by respiratory secretions--not the digestive tract.

All carnivores use acid in their stomachs to help digest their food, and this will kill some viruses. Others, however, may be robust enough to survive the digestive tract and be absorbed into the body--at which point they will cause disease. Consider norovirus, which causes nasty gastrointestinal symptoms: it can pass into the body through food contaminated with the virus. It survives the digestive system and then passes into the body, still able to cause disease.

If I were to make a short version of this answer, I would say that the danger of the virus would depend entirely upon the virus, the host, and the carnivore involved.

Here's a website that discusses the issue of virulence (how readily a virus is able to infect a host) a little further. The paper discusses bacteria, but much of what is says is still applicable to viruses:

http://pathogens.plosjournals.org/perlserv/?request=get-document&doi=10.1371%2Fj...