Past, present, and future of Japanese encephalitis

Abstract

Japanese encephalitis (JE), a vector-borne viral disease, is endemic to large parts of Asia and the Pacific. An estimated 3 billion people are at risk, and JE has recently spread to new territories. Vaccination programs, increased living standards, and mechanization of agriculture are key factors in the decline in the incidence of this disease in Japan and South Korea. However, transmission of JE is likely to increase in Bangladesh, Cambodia, Indonesia, Laos, Myanmar, North Korea, and Pakistan because of population growth, intensified rice farming, pig rearing, and the lack of vaccination programs and surveillance. On a global scale, however, the incidence of JE may decline as a result of large-scale vaccination programs implemented in China and India.

Figure 1

Contextual determinants and transmission of Japanese encephalitis.

Figure 2

Disability-adjusted life years (DALYs) per 100,000 persons in Japanese encephalitis–endemic countries. Number in parentheses indicate estimated number of deaths in 2002 according to the World Health Organization (20). NA, not available.