Rabies is commonly transmitted through the saliva of infected mammals (usually dogs) via bites. Rarely, it can occur through contamination of mucous membranes by infectious material, aerosol transmission and organ transplantation.

Incubation period: Usually 3 to 8 weeks, but could range from a few days to several years.

Infectious period: Infected person is usually not contagious; person-to-person transmission is rare.

Clinical features

Rabies usually begins with a non-specific prodrome of fever, malaise, fatigue, anorexia, cough, sore throat, abdominal pain, nausea, vomiting, or diarrhoea. The first rabies-specific symptom is pain or paraesthesia at the wound site.

The disease progresses to the acute neurological period, which manifests as either a hyperactive (furious) form in 80% with hydrophobia, aerophobia, pharyngeal spasms, opisthotonos, hyperactivity or a paralytic (dumb) form in 20% with ascending flaccid paralysis with loss of sphincter tone. Autonomic instability is often prominent (hyperthermia, salivation, hypertension and tachycardia).

The neurological phase lasts 2 to 7 days before development of coma followed by death. Fatality is virtually 100%.

Risk factors

Mammal bite occurring in a rabies-endemic country (most commonly dogs or bats).

Diagnosis

Rabies infection is a clinical diagnosis and does not depend on laboratory confirmation.

No tests are available to diagnose human rabies during the incubation period.

After onset of clinical disease, diagnostic methods include:

Direct fluorescent antibody staining of skin biopsy from nape of neck (50%)
Rabies neutralising antibodies in serum or cerebrospinal fluid (CSF)
Rabies virus isolation from saliva, CSF, urine and tracheal secretions (low)
Rabies reverse transcription polymerase chain reaction (RT-PCR) in saliva, CSF, urine and tissue
Cortical brain biopsy:
- Specimens may need to be sent overseas for tests
- Post-mortem brain examination for Negri bodies and fluorescent staining for rabies antibodies

Treatment and management

There is no specific treatment for rabies in humans.

Precaution, prevention, and control

Standard and respiratory precautions should be observed by healthcare workers caring for such patients.

Pre-exposure rabies vaccination should be discussed with persons travelling to rabies-affected countries. They should also be advised to not touch or go near mammals (including wildlife), where possible. If scratched or bitten, they should immediately wash the wound with soap and water and seek medical attention.

All mammal scratches or bite wounds should be immediately and thoroughly cleansed. If available, a viricidal agent, such as povidone iodine solution should be used to irrigate the wound.

If a patient presents with mammal scratches, bites, cuts, or wounds that have been exposed to mammal saliva in rabies-affected countries, further details regarding the signs of rabies (e.g. anxiety, agitation and aggression) should be obtained.

If there are any concerns or suspicion that the mammal may have been rabid, patients should be urgently referred to a public hospital for appropriate assessment and treatment.

Rabies post-exposure prophylaxis (rabies vaccine and immunoglobulin) should be given as soon as possible if indicated.

Notification

Who should notify:

Medical practitioners
Laboratories

When to notify:

On clinical suspicion or laboratory confirmation

How to notify:

Please refer to the Infectious Disease Notification for more information.

Notification timeline:

Immediately. No later than 24 hours from the time of diagnosis.

Resources

Animal & Veterinary Service (AVS) website on rabies in animals.