Japanese encephalitis: A very Asian travel risk
Farmers bend beneath conical hats in the bountiful rice fields that stretch across Asia like a living patchwork quilt.
It’s a rural scene as synonymous with the region as the rice crop itself is with life. And, for passing travellers, the water-logged fields are as familiar as the gaggle of giggling children, or the poultry and pigs to be found on the streets of the nearby village. But, for all their bucolic quality, rice paddies are also the breeding grounds for the Culex mosquitoes that transmit a potentially fatal seasonal disease, Japanese encephalitis (JE). In fact, JE needs more than just the mosquitoes. It can’t exist without the sharp-eyed wading birds that share the water’s bounty and the ubiquitous pigs – both of which serve as ‘hosts’ to the disease. For those Australians heading to Asia during the peak JE season - which can extend from May to as late as November - Travelvax Australia offers this profile of the disease, who is at risk and who should consider vaccination.
However, because the vaccine is expensive and the decision on whether it is warranted can involve complicated considerations, we recommend that you call a specialist travel medicine provider for advice.
If you think you may be at risk, call Travelvax’s free travel health advice and information line on 1300 360 16. Make a pre-travel appointment at least 6 weeks before your departure.
What is Japanese encephalitis?
Japanese encephalitis (JE) is a single-stranded RNA virus that belongs to the genus
Flavivirus. It is closely related to the West Nile, St. Louis encephalitis, yellow fever, and dengue fever viruses.
What are its symptoms?
Japanese encephalitis affects membranes around the brain. Most JE virus infections are mild (fever and headache) or without apparent symptoms, however around 1-in-200 infections results in severe disease that starts with high fever and progresses to coma and possibly death.
How is it transmitted?
An arthropod-borne virus (arbovirus), JE is transmitted in an ‘enzootic cycle’. That is, mosquitoes usually transmit the disease to people after biting infected animals - mainly pigs and wading birds - that serve as ‘hosts’ to the virus. There is no person-to-person transmission.
Is JE common?
There are an estimated 35,000--50,000 cases of JE each year – the majority among local people living in rice-producing areas.
Are travellers at risk?
Infection is extremely rare in travellers, as most stay in major towns and cities for short stays of only two or three weeks. Travellers most likely to be at risk are those who are (1) staying longer than month, especially in rural areas during the local JE transmission season, or (2) working or studying in ANY areas in endemic countries for an extended period. For these people, an effective vaccine is available (see below).
Where is it found?
JE occurs across most of Asia and parts of the western Pacific, in 3 main areas:
China (June through October) and
Korea (May-October).
Indian subcontinent –
India (May–October, especially northern states; year-round in some southern states),
Bangladesh (May–October),
Nepal (June-October),
Sri Lanka (year-round; variable monsoon peaks), and
Pakistan (unknown).
Southeast Asia –
Myanmar (May–October),
Thailand (year-round; seasonal peaks May–October, especially in the north),
Cambodia (May–October),
Laos (June – September),
Vietnam (year-round; seasonal peaks May–October, especially in the north),
Malaysia (year-round transmission; peak Oct–Dec in
Sarawak),
Indonesia (year-round; peak season varies by island;
Bali year-round), and the
Philippines (unknown; probably year-round).
(JE also occurs occasionally in
Japan, Taiwan, Singapore, Hong Kong, Eastern Russia, Guam, Saipan and
Brunei Darussalam during the wet and early dry seasons. More recently it has become established in
Papua New Guinea and the
Torres Strait Islands, with sporadic cases in Northern Australia ,
Cape York.)
Should I consider getting vaccinated?
You should consider vaccination if you are spending a month or more in rural areas of Asia or Papua New Guinea (particularly if travel to PNG is during the wet season). However, as JE has occurred in travellers after shorter periods of travel, JE vaccination should be considered for shorter-term travellers, particularly if:
- travel is in rural areas during the wet season
- there is considerable outdoor activity, and/or
- your accommodation is not mosquito-proof
Vaccination may also be recommended for other travellers spending a year or more in Asia (except Singapore), even if much of the stay is in urban areas.
About the vaccine: The inactivated vaccine is given in two doses a month apart. Its high-level protection (96%) lasts for at least 2 years – probably longer. It is licensed only for adults (18 years and over). Learn more.
What else can I do to avoid the risk of JE?
PREVENT INSECT BITES: Whether or not you are vaccinated against JE, preventing insect bites is paramount – especially as malaria, dengue fever and Chikungunya fever may also be present. Use an effective mosquito repellent, wear protective clothing (loose-fitting, long-sleeved shirts and long pants), and try to stay indoors at twilight and after dark. If your accommodation does not have insect screens or air conditioning, use a mosquito net impregnated with Permethrin or Deltamethrin (which are available from Travelvax clinics) as well as mosquito coils and aerosol insecticides as necessary. Learn more.
Learn more about JE (CDC) and call Travelvax on 1300 360 164 for more free advice on staying health while travelling overseas.
