The incubation period (the time the virus spreads from the peripheral nerves near the site of the bite via the spinal cord to the brain – see transmission and pathogenesis) ranges in general between 2 and 3 month (2 weeks to 6 years are reported) depending on the site of infliction, the amount of virus and the virus strain. Due to its neurotropism all known lyssaviruses cause severe neurological symptoms as a result of an acute encephalitis. Therefore, clinical signs in humans and animals are very similar.

The infection progresses in a predictable manner, from the initial prodormal phase to the manifest as furious or paralytic forms of rabies; the outcome is almost always fatal.

Humans

After (bite) exposure with a rabid animal, initial symptoms of rabies are of non-specific nature and may be very similar to those of other infectious diseases including general weakness or discomfort, fever, or headache. A first specific clinical sign is neuropathic pain or a prickling or itching sensation at the site of the bite. Signs rapidly progress and include cerebral dysfunction, anxiety, confusion, agitation, delirium, abnormal behavior, hallucinations, and insomnia. Once clinical signs of rabies appear, without intensive care, death occurs within 2 weeks after onset of symptoms. There is no treatment available.

Animals

Infected animals start developing nonspecific signs. Usually they stop eating and drinking, withdraw, may be lethargic, or showing fever, vomiting, and anorexia. Due to rapid progression of disease the animal may become vicious or begin to show signs of paralysis. Clinical signs include cerebral and cranial nerve dysfunction, ataxia, weakness, paralysis, seizures, difficulty breathing, difficulty swallowing, excessive salivation, abnormal behavior, and aggression.

Some rabid animals tend to get aggressive biting at anything, while others are be somnolent and only bite as soon as people get close to them in an tempt to look what is wrong with them. Rabies with atypical clinical signs is increasingly recognized and clinical signs of rabies may vary greatly from one animal to another. Once the animals show severe signs they die within 6 to 5 days.

If you have no imagination about how rabies manifests clinically and want to learn about the signs of rabies in animals, in particular dogs, watch this video from Mission Rabies entitled ‘A master of deception - the signs of rabies in dogs’ https://www.youtube.com/watch?v=keeigDzDf34