japanese encephalitis: epidemiology of the disease -...
TRANSCRIPT
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
DieSevere
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
Distribution of encephalitis cases by age group Andhra Pradesh, India, 2000
6
136
201
00
50
100
150
200
250
Under 1 yr 2 to 5 yrs 6 to 15 yrs 16+ yrs
Num
ber
of C
ases
Distribution of encephalitis cases by age group Nepal, 2004
734
267356
170
150100200300400500600700800
Under 1 yr 1 to 4 yrs 5 to 9 yrs 10 to 14 yrs 15+ yrs
Num
ber
of C
ases
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: www.JEproject.org