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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

J10, J11 Influenza


Surveillance of influenza is essential for the early detection and evaluation of new variants or subtypes of influenza virus. The early detection and characterization of these viruses allows for timely annual updates of a vaccine that can prevent deaths and alleviate illness in vulnerable groups of the population.


Clinical case definition

A person with sudden onset of fever of >38°C and cough or sore throat in the absence of other diagnoses.

Laboratory criteria for diagnosis

Virus isolation:

Swab or aspirate from the suspected individual, or
Direct detection of influenza viral antigen.

Serology: Fourfold rise in antibody titre between early and late serum.

Case classification

Suspected: A case that meets the clinical case definition.

Confirmed: A case that meets the clinical case definition and is laboratory-confirmed (used mainly in epidemiological investigation rather than surveillance).


Routine weekly (at least for the epidemic period) reporting to central level of case-based or aggregated data.


• Suspected/confirmed cases by sentinel practices (general practitioners/health institutions)

• Cases confirmed by laboratory

Other sources of data (hospitals, clinics, emergency rooms, laboratories, vital statistics offices) can also be used.

International: weekly aggregated data on confirmed cases from countries to WHO (FluNet) with information on extent of activity in the community.


Case-based data for reporting


• Case classification (suspected/confirmed)
• Subtype of virus (if known)
• Date of onset
• Vaccination status if available

Aggregated data for reporting


• For every geographical area (country) and every week: number of cases by age groups, by subtype of virus (if known), by outcome

Case-based laboratory data


• Laboratory number, specimen date (day/month), patient age (years or months), city, state or province of origin of patient, isolation system, type, subtype, isolate designation, similarity to reference strain (Y/N), whether further identification in progress (Y/N), whether sample forwarded to WHO Collaborating Centre (Y/N).


Graphs: Number of cases by week, by age group, by virus subtype.

Tables: Number of cases by week, by age group, by geographical area, by virus subtype, by outcome.

Maps: Number of cases by week, by geographical area, by country.



• Rapid isolation and antigenic characterization of influenza viruses in order to help plan the formulation of vaccine for the following season

• Early detection of influenza epidemics in order to assist in the implementing public health control measures (vaccines have to be given before the onset of an epidemic) and in planning for the possible impact of disease on essential services

• Morbidity and mortality data to estimate the impact and costs of the outbreak


The speedy provision of isolates to the WHO Collaborating Centres is crucial.

Laboratory surveillance is most specific and is the cornerstone of surveillance.

Sentinel surveillance (by general practitioners) on influenza-like illness is less specific but sensitive and rapid.


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: lavanchydt@who.ch / outbreak@who.ch
Tel: (41 22) 791 2656/2850/2111
Fax: (41 22) 791 4878/0746 attn CSR
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