Rabies is a lethal viral infection of the brain and nervous system. Human infection most commonly occurs via the bite of a rabid animal. Rabies has a prolonged incubation period--the time from infection to the onset of symptoms. Dr. Jatin Vyas notes in a National Library of Medicine Medline Plus online entry that the average incubation period for rabies is three to seven weeks. Once the symptoms of rabies emerge, the illness is almost uniformly fatal.
Fever, Headache and Fatigue
The initial symptoms of rabies emerge when the virus reaches the central nervous system, which includes the brain and spinal cord. Symptoms are deceptively unremarkable in the first few days of the illness and include fever, chills, headache and fatigue. The initial flu-like phase of rabies, or the prodrome, typically lasts approximately 2 to 10 days, according to the medical reference text "Principle and Practice of Infectious Diseases."
Nausea, Vomiting and Diarrhea
Penn State College of Medicine's Milton S. Hershey Medical Center notes that gastrointestinal symptoms such as nausea, vomiting, diarrhea and abdominal pain may occur along with other flu-like symptoms during the prodromal phase of rabies.
Pain at Infection Site
As noted by Dr. Vyas in the Medline Plus entry on rabies, pain at the healed wound site where the rabies virus entered the body may be a symptom of the illness. While this symptom does not uniformly occur, it proves significant because it is typically the only clue pointing to rabies during the prodromal phase of the illness.
Difficulty Swallowing, Hydrophobia and Excessive Salivation
As patients progress from the prodromal to the neurological phase of rabies, signs and symptoms characteristic of the illness emerge. The muscles of the throat and esophagus exhibit periodic spasms, causing swallowing difficulty, notes the Centers for Disease Control and Prevention. Attempts to drink typically provoke these spasms. The reaction proves so severe that sufferers are said to fear water, a symptom known as hydrophobia. Additionally, the salivary glands produce excessive saliva with rabies. The excess saliva combined with swallowing difficulties leads to drooling.
Agitation, Anxiety and Confusion
"Principles and Practice of Infectious Diseases" states that most patients develop hyperactive symptoms during the neurological stage of rabies. Agitation, restless, confusion, anxiety, excitability, thrashing, intermittent seizures and bizarre behavior may occur, interspersed with periods of relative calm.
Progressive Paralysis
The hyperactive symptoms of rabies give way to muscle weakness that progresses to paralysis. Some patients do not experience hyperactive symptoms, but rather begin developing paralytic symptoms after the prodromal phase of the illness. On average, the neurological phase of rabies persists for 2 to 7 days, according to "Principles and Practice of Infectious Diseases."
Coma
The neurological phase of rabies transitions to coma and death. While exceedingly rare, a few people have survived rabies. All survivors had been previously immunized against rabies before contracting the illness.
References
- Centers for Disease Control and Prevention: Rabies, Information for Doctors
- Centers for Disease Control and Prevention: What Are The Signs and Symptoms of Rabies?
- World Health Organization: Rabies
- Penn State College of Medicine Milton S. Hershey Medical Center: Rabies
- "Principles and Practice of Infectious Diseases, Sixth Edition"; Gerald L. Mandell, M.D., et al., Editors; 2004
