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Rabies

Rabies remains a widespread disease throughout the world, responsible for tens of thousands of deaths every year. Most often, it is transmitted by dogs. In Europe, bats, which host different viruses from those of dogs or foxes, are increasingly monitored. The disease is fatal in the absence of treatment: people having been in contact with suspect animals are thus systematically treated (there were more than 4,000 treatments in France in 2006).


Epidemiology

Rabies is the cause of about 55,000 deaths every year worldwide, most often following an infection transmitted by a rabid dog. Each year, around 10 million people receive treatment after exposure to animals in which rabies is suspected. According to the WHO, "the assessment shows that this public health responsibility weighs largely on Asia (with an estimate of 31,000 deaths), although the estimate for Africa (24,000) is much higher than was initially thought. It is also Asia that bears 96.5% of the economic weight of rabies over developing countries, spending 560 million dollars each year mainly for post-exposure prophylaxis."

No case of human rabies acquired in French territory has been reported since 1924. However, human cases acquired outside French territory and diagnosed in France have been registered (see the chapter: Rabies in France in 2007). Therefore, precautions are to be taken with regard to wild and domestic animals for travellers in endemic regions: Asia, Africa, Central Europe, the Middle East, and South America.


The disease

The rabies virus (genus Lyssavirus) is present in the saliva of the animal (dog, wild animal...) at the end of the disease. It should be remembered that rabies is not a disease that is contagious from human to human (except in cases of organ transplants or grafts). Humans and animals are most often infected by bites, scratches, or licking of the excoriated skin or of a mucous membrane. The rabies virus is neurotropic: it modifies the operation of the nervous system. It does not cause lesions that are physically visible in the brain, but disrupts neurons, especially those that regulate rhythmic operations like cardiac activity or breathing. After a few days to a few months of incubation, the affected individual develops a clinical picture of encephalitis. The symptomatic phase often begins with a dysphagia (difficulty in swallowing) and various neuropsychiatric disorders, especially anxiety and agitation. Hydrophobia is sometimes present. The disease develops towards a coma and death (often by respiratory arrest) in a few days to a few weeks. The outcome is always fatal in the absence of post-exposure treatment or when the disease is overt.
In 2004, however, a young American woman survived rabies. She had been bitten by a bat and had received no post-exposure treatment. She underwent serious treatment in the intensive care unit. She survived and recovered with few after-effects. While the survival of this young woman opened prospects with regard to treatment, the reason for her survival remains unknown. In fact, among the approximately ten patients treated the same way since, none has survived.


Treatment

Post-exposure treatment begins with nonspecific treatment: cleaning of the wounds, antibiotic therapy, tetanus prophylaxis. It is followed by a specific, well-tolerated treatment, which includes vaccination, with a rabies serotherapy in some cases, and must be performed as quickly as possible after exposure, before the appearance of the first symptoms, which signals an inexorably fatal development. It consists of 4 or 5 intramuscular injections spread over a month.
In 2006 in France, nearly 4,300 people received post-exposure treatment. This does not mean that these people had been infected, rather that a suspicion existed, entailing that the precautionary principle be applied.

 


At the Institut Pasteur

The National Reference Centre for Rabies at the Institut Pasteur, along with the Collaborating Centre for the WHO, maintains epidemiological surveillance of rabies in France. Each year it performs more than a thousand analyses on suspect human or animal samples, and coordinates the vast network of Rabies Treatment Centres (66 centres and 21 posts spread across French territory). The Rabies Treatment Centre of the Institut Pasteur’s Medical Centre provided more than 900 consultations in 2006; 60% of these patients received a rabies treatment. At the same time, three research laboratories (Lyssavirus Dynamics and Host Adaptation Unit, Antiviral Strategies Unit, and the Neuro-Immuno Virology Laboratory) are conducting complementary research on the rabies virus and the disease.