Lyssavirus of the family Rhabdoviridae.
Rabies is a zoonotic disease affecting a wide range of domestic and wild mammals, including bats. The virus is present primarily in the saliva, and infection of humans usually occurs through the bite of an infected animal, usually a dog, which may not show signs of rabies. Transmission may occasionally occur also through other contact with a rabid animal, for example following a penetrating scratch with bleeding, or through licking of broken skin and mucosa. Laboratoryconfirmed person-to-person transmission other than via organ transplant has not been reported.
Nature of the disease
Rabies is an acute viral encephalomyelitis, which is almost invariably fatal. The initial signs include a sense of apprehension, headache, fever, malaise and sensory changes around the site of the animal bite. Excitability, hallucinations and abnormal fear of drafts of air (aerophobia) are common, followed in some cases by fear of water (hydrophobia) due to spasms of the swallowing muscles, progressing to delirium, convulsions and death a few days after onset. A less common form, paralytic rabies, is characterized by paralysis and loss of sensation, weakness and pain.
Rabies is present in mammals in most parts of the world (see map). Most of the estimated 55 000 human rabies deaths per year occur in Africa and Asia.
Risk for travellers
The risk to travellers in areas where rabies occurs (see map, or http://www.who.int/rabies/rabnet/en) is proportional to the probability of contact with potentially rabid mammals. In most developing countries, the estimated ratio of dogs, both owned and ownerless, to humans is 1:10 and an average 100 suspected rabid dog bites per 100 000 inhabitants are reported annually. As rabies is a lethal disease, medical advice should be sought immediately at a competent medical centre – ideally, the rabies treatment centre of a major city hospital. First-aid measures should also be started immediately (see “Post-exposure prophylaxis”, below).
Travellers should avoid contact with free-roaming animals, especially dogs and cats, and with wild, free-ranging or captive animals. For travellers who participate in caving or spelunking, casual exposure to cave air is not a concern, but cavers should be warned not to handle bats. In most countries of the world, suspect contact with bats should be followed by post-exposure prophylaxis.
The map shows the WHO categories of risk, from no-risk (rabiesfree) countries or areas to countries or areas of low, medium and high risk (dog rabies). Categorization is based primarily on the animal host species in which the rabies virus is maintained, e.g. bats and/or other wildlife and/or dogs, and on the availability of reliable laboratory-based surveillance data from these reservoir species. Access to proper medical care and the availability of modern rabies vaccines have also been taken into consideration on a country basis. In countries belonging to categories 2–4 (see below), pre-exposure immunization against rabies is recommended for travellers with certain characteristics:
Category 1: no risk.
Category 2: low risk.
In these countries travellers involved in activities that might bring them into direct contact with bats (for example, wildlife professionals, researchers, veterinarians and adventure travellers visiting areas where bats are commonly found) should receive preexposure prophylaxis.
Category 3: medium risk.
In these countries, travellers involved in any activities that might bring them into direct contact with bats and other wild animals, especially carnivores, (for example, wildlife professionals, researchers, veterinarians and travellers visiting areas where bats and wildlife are commonly found) should receive pre-exposure prophylaxis.
Category 4: high risk.
In these countries, travellers spending a lot of time in rural areas and involved in activities such as running, bicycling, camping or hiking should receive pre-exposure prophylaxis. Prophylaxis is also recommended for people with significant occupational risks, such as veterinarians, and expatriates living in areas with a significant risk of exposure to domestic animals, particularly dogs, and wild carnivores. Children should be immunized as they are at higher risk through playing with animals, particularly with dogs and cats; they may receive more severe bites and are less likely to report contact with suspect rabies animals.