A new study from Philippines researchers says that Japanese encephalitis (JE) is endemic and covers a large geographic range in the country prompting them to recommend the JE vaccine be implemented as part of the national vaccine schedule.

Image/Howard the Duck
Image/Howard the Duck

The study, published in PLoS Neglected Tropical Diseases Friday, looked at the burden and epidemiology of JE, which up to this point was not well define, and conducted searches on Japanese encephalitis and the Philippines in four databases and one library. Data from acute encephalitis syndrome (AES) and JE surveillance and from the national reference laboratory from January 2011 to March 2014 were tabulated and mapped.

The researchers from the University of the Philippines Manila—National Institutes of Health, Institute of Child Health and Human Development, Manila, Philippines, the Philippines Department of Health, the Research Institute for Tropical Medicine (RITM) and the World Health Organization Regional Office of the Western Pacific, Manila, Philippines concluded based on the review, Japanese encephalitis virus (JEV) is an important cause of encephalitis and febrile illness in all three major island groups of the country and confirming that JE has an extensive geographic distribution in the Philippines. The majority of cases were seen in children younger than 15 years and males were more often affected than females.

These findings support the introduction of JE vaccine into the country’s routine immunization program.

They note that continued and improved surveillance with laboratory confirmation is needed to systematically quantify the burden of JE, to provide information that can guide prioritization of high risk areas in the country and determination of appropriate age and schedule of vaccine introduction, and to measure the impact of preventive measures including immunization against this important public health threat.

Japanese encephalitis is a vector-borne disease that is endemic in most of Asia. Worldwide, it is estimated that around 68,000 cases occur annually, 40,000 in the Western Pacific Region alone. Most of these cases in endemic countries occur among children under 15 years of age, as adults are often already immune to the disease. JE is a significant public health threat, with case fatality rates of up to 30% and long-term neuropsychological sequelae in 30–50% of its survivors.