Japanese Encephalitis: Epidemiology and Current Perspectives in Vaccines

Japanese encephalitis is a major cause of encephalitis in Asia. An estimated 50 000 cases occur in largely rural areas of the south and east Asian region resulting in significant morbidity and mortality. While the disease has declined in Japan, South Korea, Thailand and China, it has extended in other parts of the region, including India and Nepal. Diagnosis of the disease is largely based on clinical signs and symptoms, and treatment remains supportive. Further work is needed to provide rapid reliable diagnostics and improved surveillance. Vaccination is the mainstay of preventing serious disease in humans. The mouse brain derived vaccine is the most widely used vaccine though there are safety concerns. A live (SA 14-14-2) vaccine is increasingly being used though regulatory issues around production need to be resolved. There are also promising new vaccines undergoing clinical trials that show potential for wide scale use. Vaccine schedules, surveillance of adverse events, and setting up effective vaccination programmes are important issues that need addressing to maximise the impact of the available vaccines.