The infected mosquito, which feeds outdoors from dusk to dawn, is present In temperate areas; in greatest numbers from June through September. Rural and agricultural areas are the most frequent sites of transmission, in particular where flooding irrigation is employed. However, in many areas of Asia, given the appropriate ecological conditions, transmission occurs near or even in urban settings.

Most infections are asymptomatic. Children and adults >50 years of age are at greatest risk of typical encephalitis, which occurs in about 1 of 250 infections. The onset is sudden, usually with fever, headache and seizures and encephalitis or meningitis. The mortality rate with encephalitis is about 30%; up to 50% of survivors have neuropsychiatric sequelae. Treatment is supportive.

Vaccination:

JESPECT is an inactivated vaccine, that is indicated for individuals aged 18 years and over, who plan to reside in JE endemic areas, travel to endemic areas, particularly during transmission seasons and epidemics or those who work with JE in labs, military personnel, and lastly Torres Strait inhabitants.

The vaccine is contra-indicated in persons who have had a serous reaction to this vaccine or any of its components, particularly aluminium hydroxide. It is not licensed in children, as there is not sufficient data for its use.

Persons receiving this vaccine, will have 2 doses administered 28 days +/- 4 days apart and protection is 2 weeks following the second dose. The timing of the booster is yet to be determined. Anyone previously vaccinated with alternative JE vaccinations (such as JEVAX) will require 2 doses, until booster data becomes available.