What is JE?
Japanese Encephalitis (JE) is one of the most common causes of viral encephalitis in Asia with over 70,000 clinical cases reported worldwide every year. JE may be underreported due to inadequate surveillance in many Asian countries where the virus is endemic.1,4
How is JE transmitted?
Pigs and birds are efficient amplification and reservoir hosts for JE virus, providing a source of infection for the dead-end hosts: humans and horses who cannot transmit the disease further.1,9
- The JE virus is transmitted to humans through the bite of infected Culex mosquitoes, which breed in standing water, often in farms and rice paddies in most rural areas of Asia.6
- Culex mosquitoes tend to bite mostly at dusk and dawn, and outdoors more than indoors.10
The mosquitoes are found year-round in tropical areas and during the months of May through October in temperate areas.5
Where does JE occur?
Your patients may be at risk of JE while they travel in Asia
JE is one of the most common causes of viral encephalitis in Asia and may be underreported due to inadequate surveillance in many Asian countries where the virus is endemic.11
Unvaccinated travellers from non-endemic countries of any age may be affected.6
For most travellers to Asia, the risk for JE is low but varies on the basis of destination, season, length of stay, and activities.5
Not just Japan
While the first case of JE disease was documented in 1871 in Japan, the JE virus has also been identified throughout Asia, and it may be more appropriate to think of JE as an Asian encephalitis. The JE virus is endemic to more than 24 countries across Asia, Southeast Asia, and parts of the western Pacific.4,6
Papua New Guinea
Western Pacific Islands
Anyone traveling to Asia should be assessed for risk and educated about JE prevention strategies.
Not just in rural areas
In the past, Japanese Encephalitis was thought of as occurring only in rural areas. However, in two studies conducted in the Kurnool district of Andhra Pradesh (India) and in Can Tho City (Vietnam), it was found that the risk for Japanese Encephalitis virus transmission may be shifting, as the boundaries between rural and urban areas are blurred.12,13
Consequences of JE
The majority of infections in humans are asymptomatic, and overt encephalitis occurs in only one out of every 50-1,000 individuals infected.1
Symptomatic JE can lead to death or have devastating long-term consequences
Summary of outcomes of symptomatic JE
Adapted from IXIARO® Product Monograph
Complications of JE can include:15
- mental retardation
- convulsive disorder
- convulsions in children
- Parkinsonian syndrome
- neuropsychiatric sequelae
- paralysis of the upper extremities
When does JE occur?
Many cases of JE occur during rainy season, and these months vary by country.6 Travellers to Asia may also be bitten outside of rainy season and transmission of the JE virus can occur year-round.16 Environmental factors such as global warming can play a key role in mosquito-borne transmission, increasing favorable breeding conditions.17
Though the number of JE cases in travellers to Asia reported to the Centers for Disease Control & Prevention is few, JE does occur and consequences of the disease are potentially devastating.
- Over 70,000 symptomatic cases of JE are estimated to occur each year in Asia.1
- JE is the most common vaccine-preventable encephalitis in Asia and the leading cause of viral-induced neurologic sequelae.4
- Data show that more than one-third of travellers who developed JE were short-term travellers to Asia.2