Japanese encephalitis is a common infectious disease in Vietnam, with peak occurrences during the summer months, from may to october.

The World Organization for Animal Health (WOAH) states that the japanese encephalitis virus circulates between culex mosquitoes, pigs, and wild birds. Pigs are common vectors, spreading the virus to humans through bites from culex mosquitoes, which thrive in rice fields, animal pens, and ponds.

Pigs are a significant source of japanese encephalitis infection. In endemic areas, up to 80% of pig herds can be infected. Once infected, the virus rapidly enters the pig's bloodstream, remaining for two to four days at levels sufficient for mosquitoes to transmit it to humans.

Pigs are not the only source of japanese encephalitis pathogens. Photo: Vecteezy

Infected pigs often show no symptoms, though pregnant pigs may miscarry or have stillbirths. Laboratory studies indicate pigs can also spread the virus through respiratory secretions, increasing transmission risk within herds even without culex mosquitoes.

Besides pigs, wild birds like herons, egrets, sparrows, and ducks serve as natural virus reservoirs. Migratory birds can carry the virus, which culex mosquitoes then transmit to humans after feeding. Consequently, the risk of disease persists even in areas without pigs. Ha Noi and TP HCM have recently reported cases.

Japanese encephalitis has a mortality rate of about 30%. Among survivors, 50% experience severe sequelae including paralysis, speech loss, convulsions, epilepsy, or mental disorders. Last may, Thanh Hoa reported the death of a 14-year-old unvaccinated child.

You should prevent mosquito bites and get fully vaccinated. Check your immunization schedule or visit a vaccination center near you for a doctor's consultation.

Vietnam offers several japanese encephalitis vaccines for children and adults. The Vietnamese-produced Jevax vaccine is part of the Expanded Program on Immunization and private services. After completing the three basic doses, children need a booster shot every three years.

The Jeev vaccine (India) requires two doses, one month apart, for individuals aged 12 months to 49 years. Boosters may be needed during outbreaks or before traveling to endemic areas.

The new generation Imojev vaccine (Thailand) offers a simpler schedule for individuals aged 9 months and older. Children from 9 months to under 18 years receive two doses, one year apart. Adults aged 18 and above require a single dose. This vaccine does not need boosters. For those finding the three-year Jevax booster schedule challenging, switching to Imojev can complete their immunization course.

In addition to japanese encephalitis, you should also consider vaccines for common summer diseases such as flu, pneumococcal disease, dengue fever, and meningococcal disease.

Doctor Nguyen Van Mac Toan

Medical Manager, VNVC Vaccination System

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