Fact Sheet N°99
Updated September 2010
Rabies is a zoonotic disease (a disease that is transmitted to humans from animals) that is caused by a virus. The disease infects domestic and wild animals, and is spread to people through close contact with infected saliva via bites or scratches.
Rabies is present on all continents with the exception of Antartica, but more than 95% of human deaths occur in Asia and Africa. Once symptoms of the disease develop, rabies is nearly always fatal.
The incubation period for rabies is typically 1–3 months, but may vary from <1 week to >1 year. The initial symptoms of rabies are fever and often pain or an unusual or unexplained tingling, pricking or burning sensation (paraesthesia) at the wound site.
As the virus spreads through the central nervous system, progressive, fatal inflammation of the brain and spinal cord develops.
Two forms of the disease can follow. People with furious rabies exhibit signs of hyperactivity, excited behaviour, hydrophobia and sometimes aerophobia. After a few days, death occurs by cardio-respiratory arrest.
Paralytic rabies accounts for about 30% of the total number of human cases. This form of rabies runs a less dramatic and usually longer course than the furious form. The muscles gradually become paralyzed, starting at the site of the bite or scratch. A coma slowly develops, and eventually death occurs. The paralytic form of rabies is often misdiagnosed, contributing to the underreporting of the disease.
No tests are available to diagnose rabies infection in humans before the onset of clinical disease, and unless the rabies-specific signs of hydrophobia or aerophobia are present, the clinical diagnosis may be difficult. Post mortem, the standard diagnostic technique is to detect rabies virus antigen in brain tissue by fluorescent antibody test.
People are infected through the skin following a bite or scratch by an infected animal. Dogs are the main host and transmitter of rabies. They are the source of infection in all of the estimated 55 000 human rabies deaths annually in Asia and Africa.
Bats are the source of most human rabies deaths in the United States of America and Canada. Bat rabies has also recently emerged as a public health threat in Australia, Latin America and western Europe. Human deaths following exposure to foxes, raccoons, skunks, jackals, mongooses and other wild carnivore host species are very rare.
Transmission can also occur when infectious material – usually saliva – comes into direct contact with human mucosa or fresh skin wounds. Human-to-human transmission by bite is theoretically possible but has never been confirmed.
Rarely, rabies may be contracted by inhalation of virus-containing aerosol or via transplantation of an infected organ. Ingestion of raw meat or other tissues from animals infected with rabies is not a source of human infection.
Effective treatment soon (within a few days, but as soon as possible) after exposure to rabies can prevent the onset of symptoms and death.
Post-exposure prevention consists of local treatment of the wound, administration of rabies immunoglobulin (if indicated), and immediate vaccination.
Removing the rabies virus at the site of the infection by chemical or physical means is an effective means of protection. Therefore, prompt local treatment of all bite wounds and scratches that may be contaminated with rabies virus is important. Recommended first-aid procedures include immediate and thorough flushing and washing of the wound for a minimum of 15 minutes with soap and water, detergent, povidone iodine or other substances that kill the rabies virus.
The recommended post-exposure prophylaxis depends on the type of contact with the suspected rabid animal (see table).
|Table: Recommended post-exposure prophylaxis for rabies infection|
|Category of exposure to suspect rabid animal||Post-exposure measures|
|Category I – touching or feeding animals, licks on intact skin (i.e. no exposure)||None|
|Category II – nibbling of uncovered skin, minor scratches or abrasions without bleeding||Immediate vaccination and local treatment of the wound|
|Category III – single or multiple transdermal bites or scratches, licks on broken skin; contamination of mucous membrane with saliva from licks, exposures to bats.||Immediate vaccination and administration of rabies immunoglobulin; local treatment of the wound|
Other factors that should be taken into consideration when deciding whether to initiate post-exposure prevention include:
In developing countries, the vaccination status of the suspected animal alone should not be considered when deciding whether to initiate prophylaxis or not.
Dog rabies potentially threatens over 3.3 billion people in Asia and Africa. People most at risk live in rural areas where human vaccines and immunoglobulin are not readily available or accessible.
Poor people are at a higher risk, as the average cost of rabies post-exposure prophylaxis after contact with a suspected rabid animal is US$ 40 in Africa and US$ 49 in Asia, where the average daily income is about US$ 1–2 per person. In India, 20 000 rabies deaths (that is, about 2/100 000 population at risk) are estimated to occur annually; in Africa, the corresponding figure is 24 000 (about 4/100 000 population at risk).
Although all age groups are susceptible, rabies is most common in children aged under 15; on average 40 % of post-exposure prophylaxis regimens are given to children aged 5–14 years, and the majority are male.
Anyone in continual, frequent or increased danger of exposure to rabies virus – either by nature of their residence or occupation – is also at risk. Travellers with extensive outdoor exposure in rural high-risk areas where immediate access to appropriate medical care may be limited should be considered at risk regardless of duration of their stay. Children living in or visiting rabies-affected areas are at particular risk.
Rabies is a vaccine-preventable disease. The most cost-effective strategy for preventing rabies in people is by eliminating rabies in dogs through vaccination. Vaccination of animals (mostly dogs) has reduced the number of human (and animal) rabies cases in several countries, particularly in Latin America. However, recent increases in human rabies deaths in parts of Africa, Asia and Latin America suggest that rabies is re-emerging as a serious public health issue.
Preventing human rabies through control of domestic dog rabies is a realistic goal for large parts of Africa and Asia, and is justified financially by the future savings of discontinuing post-exposure prophylaxis for people.
Safe, effective vaccines also exist for human use. Pre-exposure immunization in people is recommended for travellers to high-risk areas in rabies-affected countries, and for people in certain high-risk occupations such as laboratory workers dealing with live rabies virus and other lyssaviruses, and veterinarians and animal handlers in rabies-affected areas. As children are at particular risk, their immunization could be considered if living in or visiting high risk areas.
WHO promotes wider access to appropriate post-exposure treatment using modern tissue culture or avian embryo-derived rabies vaccines through:
For more information contact:
WHO Media centre
Telephone: +41 22 791 2222