Rabies is a deadly infectious disease in animals caused by a bullet-shaped, enveloped virus. People are occasionally infected and, once infection is established in the central nerve system (CNS), the outcome is almost invariably fatal.
National Rabies Day in South Africa
Because of the seriousness and danger of rabies, the National Rabies Advisory Group of South Africa organises a National Rabies Week in association with World Rabies Day on 8 September 2009. Activities will take place during the week of 3 to 9 September. An awareness programme will be driven by the State Veterinary offices in all the areas at local level, including schools and clinics. Each of the nine provinces will also have a provincial ceremony involving high ranking officials and politicians to drive awareness. Pamphlets, t-shirts, banners, posters, etc are being produced. There will be a national and local media campaign in the build-up to the event.
More information on human rabies
Rabies kills around 55,000 people a year, mostly in Asia and Africa. There are only six known cases of a person surviving symptomatic rabies, and only two known cases of survival in which the patient received no rabies-specific treatment either before or after the onset of the illness.
Human rabies comes from a virus in saliva entering a bite wound caused by an infected animal, usually a rabid dog or cat. The severity of the bite determines the risk of infection. The disease does not usually spread from person to person.
Incubation
After being bitten, the virus enters small nerve endings at the site of the bite. The virus slowly travels up the nerve to reach the CNS where it replicates and then travels down nerves to the salivary glands where there is further replication. The time it takes this to happen depends upon the length of the nerve – a bite on the foot will have a very much longer incubation period than a bite in the face. The incubation period may last from two weeks to six months. Very often the primary wound is healed and forgotten by the time the symptoms are being noticed.
Symptoms
The period between infection and the first flu-like symptoms is normally two to 12 weeks, but can be as long as two years. Soon after, the symptoms expand to slight or partial paralysis, cerebral dysfunction, anxiety, insomnia, confusion, agitation, abnormal behaviour, paranoia, terror and hallucinations, progressing to delirium. The production of large quantities of saliva and tears, coupled with an inability to speak or swallow, are typical during the later stages of the disease; this can result in “hydrophobia”, in which the person has difficulty swallowing because the throat and jaw become slowly paralysed, shows panic when presented with liquids to drink and cannot quench his or her thirst. The disease itself was also once commonly known as hydrophobia, from this characteristic symptom.
Types of rabies
Furious rabies
When the virus reaches the CNS, the person presents with headache, fever, irritability, restlessness and anxiety. This may progress to muscle pains, salivation and vomiting. After a few days to a week the person may experience a stage of excitement and be wracked with painful muscle spasms, triggered sometimes by swallowing of saliva or water. Hence they drool and learn to fear water (hydrophobia). The infected person is also excessively sensitive to air blown on the face. The stage of excitement lasts only a few days before he or she lapses into coma and dies.
Dumb rabies
This form of rabies starts in the same way, but instead of progressing into excitement, the person retreats steadily and quietly downhill, with some paralysis, to death. Diagnosis of this type of rabies may easily be missed.
Prevention
Almost every infected case with rabies resulted in death until a vaccine was developed by Louis Pasteur and Émile Roux in 1885. Their original vaccine was harvested from infected rabbits, from which the nerve tissue was weakened by allowing it to dry for five to ten days. Similar nerve tissue-derived vaccines are still used in some countries, as they are much cheaper than modern cell culture vaccines. The human diploid cell rabies vaccine (H.D.C.V.) became available in 1967.
In unvaccinated humans, rabies is almost always fatal after symptoms affecting the nervous system have developed, but prompt post-exposure vaccination may prevent the virus from progressing.