If a rabies virus mutates quickly enough, it may induce infection within an hour or two. That is completely conceivable "Andreansky explained. "There have been reports of viruses changing their genetic makeup in order to adapt to new hosts. The rabies virus is an RNA virus that can be found in the saliva of infected animals. It is always transmitted when an animal bites another animal or human. In fact, this is how most cases of human rabies are caused; by biting something else and then failing to seek medical help. However, the rabies virus can also be transmitted through other means such as contact with infected tissue or fluids, especially if the person being bitten has not been vaccinated against the disease. In addition, the virus is very stable: it is known to remain active outside of a host for several hours at room temperature or longer if frozen. This makes it easy for pathogens like the rabies virus to be spread from one animal to another or from animal to human. There have been many reports of mutant forms of the virus arising through natural selection by the virus infecting animals who were previously immune to it. However, these mutants are usually killed off by the body's immune system before they have a chance to cause harm.