Although definitive diagnosis of rabies requires laboratory analysis of saliva or brain tissue, certain symptoms are strong indicators of rabies. In this state of agitation and excitability, death usually occurs from cardiac arrest or respiratory failure. If the patient survives the agitated state, excitability ceases.
Paralysis then sets in, progressing to death.
In paralytic rabies, the symptoms of excitability and agitation do not occur. Definitive diagnosis requires laboratory analysis of saliva or brain tissue, to detect the rabies virus. As a result, diagnosis is not possible during the incubation period. Definitive diagnosis is possible only late in the disease, or after death. If infection is allowed to progress to the appearance of clinical symptoms, rabies is inevitably fatal.