Rabies is a preventable viral disease of all mammals that is usually transmitted by the bite of a rabid animal. It is caused by viruses in the genus Lyssavirus and is nearly always fatal once symptoms appear. In domestic animals, the virus attacks the nervous system and infection results in an acute progressive encephalitis. The incubation period is 3-12 weeks, but can range from several days to months. Rabies virus may also be present in saliva 3-5 days prior to an animal exhibiting clinical signs.

In Maryland, rabies is most frequently found in wildlife, most commonly raccoons, foxes, skunks, and bats. Domestic animals, including livestock, are also at risk, and cats are the most frequently identified rabid domestic animal.