According to the Canadian Office of Laboratory Security, the rabies virus is "inactivated rapidly in sunlight and does not survive for long periods out of host unless protected in a cool dark area." "Rapidly" and "for long periods" are not very precise terms, but the implication clearly is that the virus can remain viable for some time outside the host under suitable (for the virus, that is) conditions. Further, saliva is not the only transmission medium. There have been at least two recent incidents of potential mass exposure to rabies from unpasteurized cow's milk; airborne transmission has been documented; and people have died from rabies as a result of organ transplants. While rabies cases in humans are nearly always the result of a bite from an infected animal, these other cases do serve to illustrate that the virus can be quite persistent outside its host in the right (again, for the virus) environment. The rabies virus causes aggressive behavior in its host, inducing the host to bite another potential host, facilitating transmission of the virus. Pretty clever, huh?