The incubation period of the disease depends on the distance the virus has to travel from the site of entry in the body upto the central nervous system. Saliva from an infected animal is the primary source of transmission. Rabies is spread when an infected animal scratches or bites another animal or human, wherein, the open wound is contaminated by infectious saliva. Seldom, has any case been reported, where, the saliva, coming into contact with the oral or respiratory passages or intact skin could cause Rabies. The dog is the most common animal involved.
Rabies virus travels from the brain to the salivary glands during the final stages of the disease, facilitating the spread the disease, especially, through a bite. The virus does not usually get across through unbroken skin. Yet, lick form an infected animal has to be viewed with caution. The disease is readily transmitted when scratches, abrasions, open wounds, or bruised mucous membranes get into contact with saliva, nervous or brain tissue from an infected animal. The Rabies virus is short lived when exposed to open air. It can only survive in saliva and dies when the animal’s saliva dries up.
Hydrophobia ("fear of water") is one of the historic names of Rabies. It ascribes to a set of symptoms in the later stages of the infection. Especially, when a Human being is affected, the person has difficulty in swallowing and panics when presented with liquids to drink. As the individual cannot quench his or her thirst, the situation becomes vey pathetic. Any mammal infected with the virus may also demonstrate hydrophobia.
Salivation is greatly increased. Coordination between facial and laryngeal muscles is impared. Attempts to drink, or even the intention or suggestion of drinking, may cause excruciatingly painful spasms of the muscles in the throat and larynx. This can be attributed to the fact that the virus cripples the facial and laryngeal nerves and multiplies and accumilates in the salivary glands of the infected animal for the purpose of further transmission through biting. The infected animal's ability to transmit the virus will reduce significantly if it is able to swallow its saliva.