Cause
The rabies virus (Lyssavirus genus) is found in the saliva of infected animals (dogs, cats, and other wild mammals) in the latter stages of the disease. It is usually transmitted through direct contact with the saliva of an infected animal through a bite, or scratch or if the animal licks broken skin or mucosa. Human-to-human transmission (through organ transplants or mother-to-fetus transmission) is extremely rare.
Symptoms
The rabies virus is neurotropic: it infects the nervous system and stops it from functioning properly. It does not cause visible lesions in the brain but it disrupts neurons, especially those regulating autonomic functions such as heart rate and breathing. After the incubation period, which can be just a few days but is more usually a few months, the infected individual develops encephalitis symptoms. The symptomatic phase often begins with dysphagia (difficulty swallowing) and various neuropsychiatric disorders, especially anxiety and agitation. The patient may develop hydrophobia (involuntary spasm of the neck and diaphragm muscles at the sight of water). Once the symptoms appear, the disease leads to coma and death within a few hours or a few days. Apart from a few described cases, the outcome is always fatal after the onset of clinical signs.
Exceptional cases of survival without post-exposure treatment
In 2004, an American teenager survived rabies. She was bitten on the American mainland by a bat and was given no antirabies vaccination before or after this exposure. After receiving aggressive treatment in intensive care, she survived and recovered with few after-effects. Although this girl's recovery opened up new possibilities for treatment, her survival cannot be attributed to the treatment she received and can probably be explained by the combination of a particularly effective immune response in this young girl and a virus that is poorly adapted to humans. Indeed, survival after proven rabies infections is rare, most often associated with severe sequelae and no curative treatment has been identified to date.
Epidemiology
Rabies is responsible for around 59,000 deaths worldwide each year, mainly in Asia and Africa, most often following a bite from a rabid dog. These deaths can be explained by the lack of implementation of disease control measures in dogs in these countries and by the great difficulties of access to post-exposure prophylaxis for the most vulnerable populations.
In France, no human cases of rabies contracted on the mainland has been reported since 1924. In 2008, a human case linked to a virus very close to those circulating in blood-feeding bats in Latin America was confirmed in French Guiana. Human cases contracted outside France have also been diagnosed within the country. The last patient to die from rabies in France (a 10-year-old child in the Lyon area) was diagnosed in October 2017, after being contaminated by a puppy in Sri Lanka. Finally, the diagnosis of rabies due to a bat lyssavirus EBLV-1 was made in 2020, after the death of a patient in 2019 in the New Aquitaine region.
It is therefore important to remember to stay away from wild animals everywhere in the world (bats, monkeys...) and never touch or feed pets in countries where dog rabies is not under control : mainly Asia and Africa, and also to a lesser extent Central Europe, the Middle East and South America.
Treatment
Preventive rabies treatment post-exposure to a suspicious animal begins with urgent cleansing of the wounds (water and soap every 15 min) then a careful application of an antiseptic (control of tetanus immunity is also recommended after a bite as well as a course of antibiotics in some cases). Post-exposure prophylaxis itself consists of a vaccination, combined with serum therapy for the more severe cases. The treatment should be administered as soon as possible after exposure, before the appearance of the first symptoms, which signal the start of an inevitably fatal decline. Prophylaxis involves 4 or 5 intramuscular injections over the course of a month and is well tolerated. Many countries also use an intradermal prophylaxis regimen recommended by WHO since 2018. It is estimated that each year, approximately 17 million people worldwide receive post-exposure rabies prophylaxis.
In 2019, 3625 people received post-exposure treatment in France, amongst which 64% were exposed abroad. This does not necessarily mean that these people had been exposed to the rabies virus, but rather that the risk of transmission could not be ruled out and prophylaxis was administered as a precaution.
February 2021
