Instructions for users This slide presentation provides an overview of the epidemiology of JE. Below many of the slides, there are notes to explain the information in the slide. You should adapt the presentation for your own use.

Japanese Encephalitis: Epidemiology of the Disease

Learning Objectives Participants will: Understand the extent and severity of the JE problem worldwide Understand the means and patterns of transmission of JE

JE virus: Virology Japanese encephalitis (JE) serocomplex — 10 viruses — 6 human pathogens (JE, West Nile, Kunjin, Usutu, St. Louis encephalitis, Murray Valley encephalitis viruses) — Most are amplified bird – mosquito – bird 4 genotypes in Asia (possibly 5)

JE virus: History of discovery 1871: “Summer encephalitis” epidemic in Japan 1924: Agent from human brain tissue isolated in rabbits 1934: Isolate of this virus produced experimental encephalitis in monkeys 1938: First isolate from Culex tritaeniorhynchus 1930s: First mouse brain-derived vaccines developed 1954: “Refined” mouse brain vaccine developed

Why is JE a problem? JE is the leading cause of viral neurological disease in Asia, now that poliomyelitis has nearly been eradicated. More than 3 billion people live in areas where JE is transmitted. Up to 50,000 cases of JE are reported to WHO each year. Up to 10,000 to 15,000 deaths are reported each year.

Cases are under-reported Cases are under-reported due to — Lack of good surveillance systems. — Lack of diagnostics. Actual number of cases is likely much higher. Photo credit: Julie Jacobson

Clinical spectrum of JE disease Die Severe Moderate Mild Asymptomatic

Death and disability from JE Up to 30% of all patients with JE die. For those that survive the illness, 30% to 75% cases are left with disability. Disability is both physical and cognitive. Photo credit: Julie Jacobson

Where does JE occur ?

Age groups affected by JE Children 1 to 15 years of age are mainly affected in endemic areas. But people of any age can be infected. Adult infection most often occurs in areas where the disease is newly introduced. Photo credit: Carib Nelson, PATH

Data supplied by Government of Andhra Pradesh Data supplied by WHO, Nepal Different patterns of age distribution of cases

Two patterns of transmission of JE 1.Seasonal pattern, with a large increase in cases at a certain time of the year (e.g., southern China) 2.Year-round pattern (e.g., Bali, Indonesia) JE may be spread: Data supplied by International Vaccine Institute

Transmission of JE JE is spread by mosquitoes. Culex tritaeniorhynchus is the main vector in most of Asia, but other species that breed in rice paddies, ditches, and ground pools are also important. Photo credit: Richard G. Weber Culex mosquito laying eggs on water

JE Transmission Cycle

People at risk People living in rural areas have the highest risk of disease because the mosquitoes that spread JE breed in rice paddies and pools of water. Cases in urban areas also occur. Photo credit: Julie Jacobson, PATH

Data from your country/region History of disease in your country. Incidence/case data. Map of JE distribution in your country. Age and sex distribution. Seasonal patterns. Local mosquito vectors and habitats. You may want to include your local data here. For example:

Acknowledgements Please include the following acknowledgement if you use this slide set: This slide set was adapted from a slide set prepared by PATH’s Japanese Encephalitis Project. For information: