Risk for Japanese Encephalitis by Country4*
Country |
Affected areas |
Transmission season |
Australia |
Outer Torres Strait islands |
December–May; all human cases reported February–April |
Bangladesh |
Presumed widespread |
Most human cases reported May–October |
Bhutan |
Very rare reports; probably endemic in nonmountainous areas |
No data |
Brunei |
Very rare reports; presumed to be endemic countrywide |
Unknown; presumed year round |
Burma (Myanmar) |
Limited data; presumed to be endemic countrywide |
Unknown; most human cases reported May–October |
Cambodia |
Presumed to be endemic countrywide |
Year round; peak season May–October |
China |
Human cases reported from all provinces except Xizang (Tibet), Xinjiang and Qinghai. |
Most human cases reported June–October |
East Timor |
Sporadic human cases reported; presumed to be endemic countrywide |
No data; cases reported year round in neighboring West Timor |
India |
Human cases reported from all states except Dadra, Daman, Diu, Gujarat, Himachal Pradesh, Jammu and Kashmir, Lakshadweep, Meghalaya, Nagar Haveli, Punjab, Rajasthan and Sikkim |
Most human cases reported May–October, especially in northern India; the season may be extended or year round in some areas, be extended or year round in some areas, especially in southern India |
Indonesia |
Presumed to be endemic countrywide |
Year round; peak season varies by island |
Japan** |
Rare sporadic human cases on all islands except Hokkaido; enzootic activity ongoing |
Most human cases reported July–October |
Korea, North |
Limited data; presumed to be endemic countrywide |
No data; proximity to South Korea suggests peak transmission is likely to be May–October |
Korea, South** |
Rare sporadic human cases countrywide; enzootic activity ongoing |
Most human cases reported May–October |
Laos |
Limited data; presumed to be endemic countrywide |
Year round; peak season June–September |
Malaysia |
Endemic in Sarawak; sporadic cases reported from all other states; occasional outbreaks reported |
Year round; in Sarawak, peak season October–December |
Nepal |
Endemic in southern Iowlands (Terai); cases also reported from hill and montain districts, including the Kathmandu valley |
Most human cases reported June-October |
Pakistan |
Limited data; human cases reported from around Karachi |
Unknown |
Papua New Guinea |
Limited data; probably widespread |
Unknown; probably year round |
Philippines |
Limited data; presumed to be endemic on all islands |
Year round; peak season June–September |
Russia |
Rare human cases reported from the Far Eastern maritime areas south of Khabarovsk |
Most human cases reported July–September |
Singapore |
Rare sporadic human cases reported |
Year round |
Sri Lanka |
Endemic countrywide except in mountainous areas |
Year round; variable peaks based on monsoon rains |
Taiwan** |
Rare sporadic human cases islandwide |
Most human cases reported May–October |
Thailand |
Endemic countrywide; seasonal epidemics in the northern provinces |
Year round; peak season May–October, provinces especially in the north |
Vietnam |
Endemic countrywide; seasonal epidemics in the northern provinces |
Year round; peak season May–October, especially in the north |
Western Pacific Islands |
Outbreaks of human disease reported in Guam in 1947–1948 and Saipan in 1990 |
Unknown; most human cases reported October–March |
*Data are based on published reports and personal correspondence. Risk assessments should be performed cautiously, because risk can vary within areas and from year to year, and surveillance data regarding human cases and JE virus transmission are incomplete. |
**In some endemic areas, human cases among residents are limited because of natural immunity among older people or vaccination. However, because JE virus is maintained in an enzootic cycle between animalsand mosquitoes, susceptible visitors to these areas still may be at risk of infection. |