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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

A95.9 Yellow fever

Case report universally required by International Health Regulations


This mosquito-borne virus disease occurs in tropical regions of Africa and South America and is maintained by sylvatic transmission of virus involving forest-dwelling mosquitoes and monkeys. Transmission to humans may occur in forest transition zones and may subsequently enter an urban cycle through Aedes aegypti. Many cities are now threatened with epidemics as yellow fever is undergoing a major resurgence especially in the African region. Surveillance data allow for monitoring disease incidence, prediction and early detection of outbreaks and monitoring of control measures.

Strategies for yellow fever control include control of Ae. aegypti in urban centres, infant immunization, vaccination campaigns, outbreak prevention, epidemic detection and control.

Case reporting is universally required by International Health Regulations.


Clinical description

Characterized by acute onset of fever followed by jaundice within 2 weeks of onset of first symptoms. Haemorrhagic manifestations and signs of renal failure may occur.

Laboratory criteria for diagnosis

Isolation of yellow fever virus, or

Presence of yellow fever specific IgM or a four-fold or greater rise in serum IgG levels in paired sera (acute and convalescent) or

Positive post-mortem liver histopathology or

Detection of yellow fever antigen in tissues by immunohistochemistry or

Detection of yellow fever virus genomic sequences in blood or organs by PCR

Case classification


Suspected: A case that is compatible with the clinical description.

Probable: Not applicable.

Confirmed: A suspected case that is laboratory-confirmed (national reference lab) or epidemiologically linked to a confirmed case or outbreak.


Routine weekly/monthly reporting of aggregated data on suspected and confirmed cases from peripheral to intermediate and central level. Zero reporting required at all levels.

Immediate reporting of suspected cases from peripheral to intermediate and central levels.

All suspected cases and outbreaks must be investigated immediately and laboratory-confirmed.

Case-based surveillance must be implemented in countries identified by WHO as being at high risk for yellow fever. Specimens must be collected to confirm an epidemic as rapidly as possible. Priority is placed on collecting specimens from new or neighbouring areas (other than the area where the epidemic is already confirmed).

International: Mandatory reporting of all suspected and confirmed cases within 24 hours to WHO.


Aggregated data for reporting

Number of cases

Doses of yellow fever vaccine administered to infants, by geographical area

Completeness/timeliness of monthly reports

Case-based data for reporting and investigation

Unique identifier

Geographical area name (district and province)

Date of birth

Date of onset

Date of notification

Date of investigation

Ever received a dose of yellow fever vaccine? (1 = yes; 2 = no; 9 = unknown)

Date acute blood specimen received in laboratory

Date convalescent blood specimen received in laboratory (if applicable)

Date histopathology specimen collected (if applicable)

Depending on which laboratory tests used:


• IgM (1 = positive; 2 = negative; 3 = no specimen processed; 9 = unknown)
• virus isolation (1 = positive; 2 = negative; 3 = no specimen processed; 9 = unknown)
• IgG (4-fold rise) (1 = positive; 2 = negative; 3 = no specimen processed; 9 = unknown)
• liver

Date IgM results first sent

Date virus isolation results first sent

Final classification

Date histopathology report first sent

Date convalescent blood specimen received in laboratory (if applicable)

Date histopathology specimen collected

Date IgG results first sent

Final classification (1 = confirmed; 2 = suspected; 4 = discarded)

Final outcome (1 = alive; 2 = dead; 9 = unknown)


Aggregated data


• Incidence rate by month, year, and geographic area
• Yellow fever vaccine coverage by year and geographic area
• Completeness/timeliness of monthly reporting

Case-based data

same as aggregated data plus the following:


• Confirmed cases by age group, immunization status, geographic area, month, year
• Case-fatality rate
• Final classification of all suspected cases




Completeness of monthly reporting


Percent of all suspect cases for which specimens were collected


If IgM test is done: Laboratory results sent ≤3 days of receipt of acute blood specimen


If virus isolation is done: results sent ≤ 21 days of receipt of acute blood specimen


If IgG test is done: results sent ≤3 days of receipt of convalescent blood specimen



* Target during non-outbreak periods. Once an outbreak is confirmed, the priority is to detect outbreaks in neighbouring areas and confirm them in the laboratory.



• Investigate suspect cases and collect laboratory specimens to confirm an outbreak and mobilize emergency immunization activities

• Monitor yellow fever vaccine coverage by geographic region to monitor progress and identify areas of poor performance so that corrective actions can be taken

• Monitor disease incidence to assess impact of control efforts


At risk for yellow fever epidemics in Africa: Angola, Benin, Burkina Faso, Burundi, Cameroon, Cape Verde, Central African Republic, Chad, Congo, Côte d'Ivoire, Democratic Republic of Congo (formerly Zaire), Equatorial Guinea, Eritrea, Ethiopia, Gabon, Gambia, Ghana, Guinea, Guinea-Bissau, Liberia, Kenya, Mali, Mauritania, Niger, Nigeria, Rwanda, Senegal, Sierra Leone, Somalia, Sudan, Tanzania, Togo, Uganda.

In America: Bolivia, Brazil, Colombia, Ecuador, Guyana, French Guiana, Panama, Peru, Surinam, Venezuela.


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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