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Japanese Encephalitis in Vietnam

Recent reports of Japanese encephalitis (JE) activity belie the fact that disease rates in Vietnam have decreased in recent years. [1,2]

Time and Place:
– Japanese encephalitis was first reported in Vietnam in 1960.
– Most cases of Japanese encephalitis in Vietnam occur in the South during the rainy and early dry season; and in the north during late summer and autumn.
– 61,729,000 persons (73% of the population) live in areas of risk.

Vaccine Schedule:
BCG – birth
DTwP – 2, 3, 4 months
HepB – birth; 2, 4 months; [since 2003]
Japanese encephalitis – 12, 13, 25 months; Part of country [selected HRD]
Measles (monovalent) – 9 months
OPV – 2, 3, 4 months
TT – pregnant women; CBAW (15-35) in some areas
Typhoid – 3-10 years; Part of country [selected HRD]
Vitamin A – 6-11, 12-17, 18-24, 31-36 months

WHO estimates for vaccine coverage decreased slightly from 95% in 2006, to 88% in 2008 (see graph).

The incidence of Japanese encephalitis has decreased dramatically during the past three decades – from a peak of 4,935 cases in 1985, to only 558 cases in 2000.
– 9,574 cases were reported during 1986 to 1990; 6,981 during 1991 to 1996.
– 68 cases were officially reported in 2009.
– Annual mortality from the disease has varied from 60 to 150 cases.

Incidence and Prevalence:
– Japanese encephalitis accounted for 67% of acute childhood encephalitis in Hanoi during the summer of 1995.
– The annual incidence among children in Southern Vietnam is 4.6% (2007 publication)
– A recent outbreak was centered in Ha Bac and Hai Hung.
– Eight children died of presumed Japanese encephalitis in Kien Giang Province in 1999.
– 200 cases were reported in the northern region during May to June, 2005.

Exported cases
– An Australian soldier acquired Japanese encephalitis in Vietnam (reported in 1975).
– In 2006, an Italian traveler developed Japanese encephalitis (nonfatal) after returning from Vietnam.
– In 2008, an American tourist contracted Japanese encephalitis (nonfatal) while in Vietnam and Cambodia.

Related diseases:
– A new arbovirus, tentatively named “Nam Dinh virus,” was implicated in several cases of encephalitis in Ha Noi and Ha Tay in 2003, and in Bac Giang Province in 2004.

References:
1. Berger SA. Infectious Diseases of Vietnam, 2010, 382 pp. Gideon e-book series, https://www.gideononline.com/ebooks/country/infectious-diseases-of-vietnam/
2. Berger SA. Japanese Encephalitis: Global Status, 2010, 51 pp. Gideon e-book series, https://www.gideononline.com/ebooks/disease/japanese-encephalitis-global-status/

Update: Posted in ProMED

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