Estimated global incidence of Japanese encephalitis: a systematic review
The global incidence of JE is unknown because the intensity and quality of JE surveillance and the availability of diagnostic laboratory testing vary throughout the world. Countries that have implemented high-quality childhood JE vaccination programmes have seen a dramatic decline in JE incidence. Although JE is reportable to the World Health Organization (WHO) by its Member States, reporting is highly variable and incomplete. In the late 1980s, Burke and Leake estimated that 50 000 new cases of JE occurred annually among the 2.4 billion people living in the 16 Asian countries considered endemic at the time (approximate overall annual incidence: 2 per 100 000).2 In the intervening two decades, despite major population growth, urbanization, changes in agricultural practices and increased use of the JE vaccine in many countries, this figure has been widely quoted, including very recently.9–13 In 2000, assuming an annual, age-group-specific incidence of 25 cases per 100 000, Tsai estimated that in the absence of vaccination 175 000 cases of JE would occur annually among Asian children aged 0–14 years living in rural areas.14 The current study used more recent, published, local or national incidence estimates and current population data to produce an updated estimate of the annual global incidence of JE.