Epidemiology
Japanese encephalitis is an arbovirosis caused by a Flavivirus (Togaviridae family), transmitted by the bites of female insects of the genus Culex.
Culex are mosquitoes that bite at night: from sunset to sunrise. The disease cannot be transmitted directly from one human to another.
A human can be infected only by the bite of a mosquito that has bitten an infected animal. The reservoirs of the virus are pigs, birds and, more rarely, horses and cattle.
Transmission is highest in rural areas (paddies) and in urban areas during the monsoon. Japanese encephalitis is present in Asia (China, Korea, Japan, Southeast Asia and eastern parts of the former Soviet Union) and in certain regions of Oceania. In endemic regions, children 3 to 15 years of age are those affected most often.
50,000 new cases per year are counted, mainly in children. In Thailand, it has become a problem, as the mortality rate is from 10 to 20 per 100,000 inhabitants per year.
Symptoms
Japanese encephalitis is generally without symptoms: 1 case in 250 to 500 is symptomatic; however, for persons who present with symptoms, it is deadly in 25% of cases.
After 4 to 14 days of incubation, the disease manifests itself as fever, with shivering, muscle pain and sometimes mental confusion and stiff neck (meningitis-like syndrome). In children, the main symptoms may be abdominal pain, vomiting and seizures (frequent in children).
Generally, there is a recovery without problems, but in certain cases, it may progress quickly to serious encephalitis with neurological disorders, motor abnormalities and coma. Children and elderly persons are most affected by the serious forms.
In women who contract the infection during the first 2 trimesters of pregnancy, there is a high risk of miscarriage.
Treatment
No specific treatment. Symptomatic treatment.
Prevention
1. Vaccination
There are 3 types of vaccines against Japanese encephalitis. The vaccine available in France is a deactivated vaccine distributed under the commercial name Isaxio.
It requires 2 subcutaneous injections at D0 et D28.The 1st infection must be performed at least 7 days before departure.
This vaccine is recommended for all travellers departing for a long period (> 1 month) to a rural area in a region where the virus is endemic, and during the summer and autumn (from May to October) in an area of epidemic. It is contraindicated in children under 1 year of age. This vaccine can only be performed in a centre that is licensed for vaccination against yellow fever. (List of licensed centres in France).
2. Prevention of mosquito bites
Prevention is mainly based on :
- wearing ample clothing that covers the body,
- use of appropriate repellent products for the body and insectide for clothing (Moustifluid High Protection Tropical Zones & Moustifluid Lotion For Fabrics and Clothing Tropical Zones),
- and repellent-sprayed mosquito nets at night (Moustifluid Lotion For Fabrics and Clothing Tropical Zones).