Instructions for users

1. 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.

2. Japanese Encephalitis: Epidemiology of the Disease

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

4. 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 • 5 genotypes in Asia (most isolates in genotype 1)

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

6. 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.

7. Cases are under-reported • Cases are under-reported due to • Lack of good surveillance systems. • Lack of diagnostics. • Actual number of cases is probably more than 175,000 per year. Photo credit: Julie Jacobson

8. Clinical spectrum of JE disease Die Severe Moderate Mild Asymptomatic

9. Death and disability from JE • Up to 30% of all patients with JE die. • For those that survive the illness, 30% to75% cases are left with disability. • Disability is both physical and cognitive. Photo credit: Julie Jacobson

10. Where does JE occur ?

11. 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

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

13. Two patterns of transmission of JE • Seasonal, called an epidemic pattern (e.g., southern China) • Year-round, called an endemic pattern (e.g., Bali, Indonesia) JE may be spread: Data supplied by International Vaccine Institute

14. 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. Culex mosquito laying eggs on water Photo credit: Richard G. Weber

15. JE Transmission Cycle

16. 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

17. Data from your country/region You may want to include your local data here. For example: • 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.

18. 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: www.JEproject.org