Rabies

Causative agent

Rabies is an acute infection of the central nervous system caused by the rabies virus. It affects mammals like dogs, cats, foxes, bats and humans.

Mode of transmission

Rabies can affect both wild and domestic animals. When humans are bitten or scratched, or when their broken skin is licked by an infected animal, the virus in the saliva of the infected animal enters the human body through the wound and travels through nerves to the spinal cord and brain, leading to inflammation. Transmission by inhalation of virus-containing aerosol or via transplantation of an infected organ is extremely rare, and there are no evidence-based reports of human rabies arising from consumption of milk or cooked meat. According to the WHO, infected dogs are responsible for the transmission to humans in up to 99% of cases.

Incubation period

The incubation period is usually 2 to 3 months, but may vary from less than 1 week to over 1 year.

Clinical features

The initial presentation of rabies may be nonspecific and include flu-like symptoms such as malaise, fever or headache, which may last for days. There may be numbness and tingling sensation around the wound. After a few days, anxiety, confusion, spasm of swallowing muscles, paralysis, coma and death will occur. There are two forms of clinical manifestations in humans, namely furious rabies (dominated by hyperactivity) and paralytic rabies (dominated by paralysis).

Management

Rabies is almost always fatal once clinical signs appear and no specific treatment is available. However, clinical rabies can be prevented through vaccination given before or immediately after an exposure.

Prevention

1. Vaccinating dogs is the most cost-effective strategy for preventing human rabies. Dog owners should make sure their dogs are licensed and vaccinated against rabies.
2. Avoid contact with stray animals, including dogs, cats and monkeys.
3. Post-exposure prophylaxis is recommended after being bitten or scratched by animal, which consists of: (1) washing wound thoroughly with liquid soap and water immediately; (2) prompt administration of effective rabies vaccine either through intramuscular or intradermal route; and (3) prompt administration of rabies immunoglobulin into and around the wound if indicated. After exposure, the public should seek medical attention at the nearest Accident and Emergency Department. If necessary, post-exposure immunisation may be given by the attending doctor.
4. Monoclonal antibodies have been demonstrated to be safe and effective against rabies overseas.
5. Pre-exposure immunisation is recommended when travelling to high-risk destination for long-stay travellers, short-stay travellers to remote rural regions without medical facilities, or travellers with extensive outdoor exposure or engaging in high-risk activities (such as hiking, trekking, cycling, animal handling and visiting bat-infested caves). Please visit the website of Travel Health Service of the Department of Health for more details.