Japanese Encephalitis

Excerpt

Japanese encephalitis, the most common preventable cause of mosquito-borne encephalitis in Asia, Australia, and the Western Pacific, poses a major public health concern throughout the Asia-Pacific region. The Culex mosquito species transmits the virus through its bite, with transmission occurring most frequently in agricultural environments, eg, farms and rice paddies, though urban transmission can occur under specific conditions. Most infections remain asymptomatic, yet patients who develop encephalitis experience substantial morbidity and mortality. Symptomatic individuals present with high fever, headache, disorientation, coma, tremors, and mental status changes resulting from cerebral inflammation. Movement disorders, neurologic deficits, and seizures frequently develop, particularly among children.

Approximately 1 in 4 symptomatic cases proves fatal. Children represent the population most often affected, while most adults living in endemic regions acquire natural immunity over time. No specific antiviral therapy exists beyond supportive care, though a safe and effective vaccine prevents infection. Vaccination remains strongly recommended for high-risk travelers to endemic regions, and many endemic countries have adopted widespread childhood immunization programs. The most reliable protection involves consistent mosquito-bite prevention. The expanding geographic distribution linked to climate change underscores the need for primary care physicians to remain familiar with Japanese encephalitis and its prevention strategies.