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close this bookWHO Recommended Surveillance Standards (WHO; 1999; 157 pages)
View the documentAcknowledgements
View the documentAcronyms
View the documentIntroduction
View the documentNational Coordination of Communicable Disease Surveillance
View the documentExplanatory notes
View the documentSurveillance activities: criteria and WHO Department
View the documentCommunicable disease contacts in Regional Offices
close this folderDiseases
View the documentB20-B21-B22-B23-B24 AIDS
View the documentA22 Anthrax
View the documentA23 Brucellosis
View the documentA00 Cholera
View the documentA81.0 Creutzfeldt-Jakob disease
View the documentA90, A91 Dengue fever (A90) including Dengue haemorrhagic fever (DHF) & Dengue shock syndrome (DSS, A91)
View the documentA36 Diphtheria
View the documentB72 Dracunculiasis (Guinea worm disease)
View the documentA98.3, A98.4 Ebola-Marburg viral diseases
View the documentA83.0 Japanese encephalitis
View the documentB74 Lymphatic filariasis
View the documentB96.3 Haemophilus influenzae type b
View the documentB15-B17 Acute viral hepatitis
View the documentB20-B24 HIV infection
View the documentJ10, J11 Influenza
View the documentA96.2 Lassa fever
View the documentA48.1 Legionellosis
View the documentB55.1, B55.2 Cutaneous leishmaniasis
View the documentLeishmania / HIV co-infections
View the documentB55.0 Visceral leishmaniasis
View the documentA30 Leprosy
View the documentA27 Leptospirosis
View the documentB50-54 Malaria
View the documentB05 Measles
View the documentA39 Meningococcal disease
View the documentA87 Viral meningitis
View the documentB73 Onchocerciasis
View the documentA37.0 Pertussis
View the documentA20 Plague
View the documentA36 Poliomyelitis
View the documentA82 Rabies
View the documentA02.0 Salmonellosis
View the documentB65 Schistosomiasis
View the documentA50-52 Syphilis
View the documentA33 Tetanus, neonatal
View the documentB56-0, B56-1 African trypanosomiasis
View the documentB57 American trypanosomiasis
View the documentA15-A19 Tuberculosis
View the documentA75.3 Scrub typhus
View the documentA95.9 Yellow fever
open this folder and view contentsSyndromes
View the documentAnnex 1 Software free and in the public domain
View the documentAnnex 2 Proposed surveillance definitions
View the documentAnnex 3 Role and use of Geographic Information Systems (GIS) and mapping for epidemiological surveillance

A83.0 Japanese encephalitis


Over a large part of East Asia, the Japanese encephalitis (JE) virus is the most common cause of encephalitis. This mosquito-borne encephalitis has a potential for outbreaks and can be associated with a high case-fatality rate. Three strategies for control based on the natural transmission cycle of Japanese encephalitis have been proposed:


• vector control
• vaccination of swine (virus-amplifying host associated with human epidemic disease)
• vaccination of humans

Surveillance should target these elements.


Clinical description

Japanese encephalitis virus infection may result in a febrile illness of variable severity associated with neurological symptoms ranging from headache to meningitis or encephalitis. Symptoms can include: headache, fever, meningeal signs, stupor, disorientation, coma, tremors, paresis (generalized), hypertonia, loss of coordination. The encephalitis cannot be distinguished clinically from other central nervous system infections.

Laboratory criteria for diagnosis


Detection of an acute phase anti-viral antibody response through one of the following:


• Elevated and stable serum antibody titres to JE virus through ELISA, haemagglutination-inhibition or virus neutalization assays or

• IgM antibody to the virus in the serum



• Detection of the JE virus, antigen or genome in tissue, blood or other body fluid by immunochemistry or immunofluorescence or PCR, or

• JE virus-specific IgM in the CSF, or

• Fourfold or greater rise in JE virus-specific antibody in paired sera (acute and convalescent phases) through IgM/IgG, ELISA, haemagglutination inhibition test or virus neutalization test, in a patient with no history of recent yellow fever vaccination and where cross-reactions to other flaviviruses have been excluded


Note: JE infections are common and the majority are asymptomatic. JE infections may occur concurrently with other infections causing central nervous system symptoms, and serological evidence of recent JE viral infection may not be correct in indicating JE to be the cause of the illness.

Case classification


Suspected: A case that is compatible with the clinical description.
Probable: A suspected case with presumptive laboratory results.
Confirmed: A suspected case with confirmatory laboratory results.


Areas where no Japanese encephalitis transmission has been detected but where the vector is present:


Surveillance for acute central nervous system syndromes; investigation of clusters with fever.

Areas where disease is endemic with seasonal variation in transmission, and areas where epidemic Japanese encephalitis is occurring:


Routine weekly/monthly reporting of aggregated data on suspected, probable and confirmed cases from peripheral to intermediate and central level.


Case-based data at the peripheral level


• Case classification (suspected/probable/confirmed)
• Unique identifier name of patient, age, sex, geographical information
• Date of onset
• Travel history over the past 2 weeks
• Hospitalization (Y/N)
• Outcome

Aggregated data for reporting


• Number of cases by age group
• Number of suspected/confirmed cases
• Number of hospitalizations and deaths


Number of cases and deaths by geographic area. Number of hospitalizations. Case-fatality rate.



• Target high risk areas for intervention
• Monitor changes in epidemiology and pattern of disease
• Monitor trends in endemic disease or re-emergence of disease
• Monitor vaccine efficacy


Epidemic transmission in temperate zones is seasonal (summer of monsoon season months).


Regional Offices

See Regional Communicable Disease contacts on section "Communicable disease contacts in Regional Offices".

Headquarters: 20 Avenue Appia, CH-1211 Geneva 27, Switzerland

Communicable Diseases Surveillance and Response (CSR)


E-mail: arthurr@who.ch / outbreak@who.ch
Tel: (41 22) 791 2658/2636/2111
Fax: (41 22) 791 48 78
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