Japanese encephalitis is caused by a Flavivirus.

Japanese encephalitis is found in almost all Asian countries and parts of the Western Pacific. It poses a threat mainly in rural agricultural regions, particularly in areas where irrigation (artificial watering of crops) is widespread, including rice paddies. It can take from 5 to 15 days for symptoms to appear. Most cases are asymptomatic.

Less than 1% of those infected develop encephalitis (swelling of the brain), which is fatal in 20-30% of cases.

Severe cases are usually characterized by a sudden onset of :

• fever
• headaches
• vomiting

Other symptoms include:

• a stiff neck
• mental confusion
• mental or behavioural changes
• general weakness
• motor disorders
• paralysis (inability to move)
• a coma
• convulsions
• nerve and brain damage that may be permanent

Source: Health Canada