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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

B57 American trypanosomiasis

(Chagas' disease)


Targeted by WHO for elimination by the year 2000 (Resolution WHA51.14), American trypanosomiasis affects 17 countries with 16-18 million infected and over 100 million individuals at risk of infection. The disease is prevalent in the northern part of South America (the Andean Region) and in Central America; almost 25 million people are at risk and there are 5 to 6 million infected. The disease is potentially fatal and non-treatable; one third of those infected become incapacitated due to cardiac damage. Infection can also be acquired through blood transfusion.

The infection can be effectively eliminated through interruption of vector transmission and systematic screening of blood donors. Elimination has been successful in some countries of the Southern Cone of South America (Argentina, Bolivia, Brazil, Chile, Paraguay and Uruguay); surveillance is necessary to monitor prevention and control measures.



Clinical description

The main clinical signs are mainly fever, malaise, hepatosplenomegaly and lymphadenopathy in the acute phase. Many patients present without clinical signs. An inflammatory response at the site of infection (chagoma) may last up to 8 weeks.

Laboratory criteria for diagnosis


• Positive parasitology (direct, xenodiagnosis, blood culture) and/or

• Positive serology for Trypanosoma cruzi antibodies (IgM) (indirect haemagglutination test (IHA), indirect immunoflourescent antibody test (IFAT), direct agglutination test (DA) and ELISA)

Case classification


Suspected: Not applicable.

Probable: (Endemic areas) a case with unexplained fever, hepatosplenomegaly and a chagoma (inflammation at site of infection).

Confirmed: A clinically compatible case that is laboratory-confirmed.

Congenital: A newborn with positive parasitology (direct, xenodiagnosis, culture).

Indeterminate: Positive serology for T. cruzi antibodies alone, no other clinical findings related to the disease (e.g in blood donors).

Chronic: Positive serology or parasitology with chronic cardiac lesions and/or enlargement of the digestive viscera and/or peripheral neuropathies.


In endemic areas, sentinel surveillance may be the only feasible method at present.

Where possible, routine surveillance should be integrated in primary health services. At peripheral level, individual patient records must be maintained. Routine monthly reporting of aggregated data from peripheral level to intermediate level. Routine biannual reporting of aggregated data to central level.

All blood donations must be screened locally. Serological surveys (standardized and periodical) for surveillance and control.



Individual patient records

Unique identifier, name, age, sex, geographical information, laboratory results.

Aggregated data for reporting


• Number of cases identified from transfusion donors
• Number of cases by age/sex/means of diagnosis
• Number of cases with positive serology
(Number of houses or communities subject to annual vector control)


Isolate-based data for reporting*

Scientific name of organism, clinical form, organ or tissue, geographical information (patient location), date of isolation, name laboratory, laboratory number of isolate, identification methods used, results.


*(WHO Technical Report Series N° 811: Control of Chagas disease. Geneva: World Health Organization, 1991: 77-78)



Graphs: Number of cases by geographical area, month, and means of diagnosis.

Maps: Number of cases by geographical area Vector control activities/geographical area/prevalence of disease.



• Monitor disease prevalence and measure the impact of disease
• Monitor control and elimination programme
• Target resources for prevention


• Control has until now depended on vertical programmes. Monitoring and surveillance have been conducted during specific surveys. To integrate the control programme into PHC requires a network of laboratory services with different facilities at different levels for diagnosis

• Because of variation in specificity of the tests, cut-off points should be defined locally using a standard serum panel, provided by the reference laboratories of the intercontinental network for standardized serology in Brazil and Argentina

• A national laboratory network should be established in each of the countries in which Chagas' disease is endemic


WHO Regional Office for the Americas (AMRO, PAHO)

Dr S. Corber, Division of Communicable Disease Prevention and Control (HCP)


Direct telephone 001 202 974-3850,
fax 001 202 974-3648 or 001 202 974-3643

Dr G. Schmunis, Coordinator, Communicable Diseases program (HCP/HCT)


Direct telephone 001 202 974 32 72
Fax 001 202 974 36 88

Dr. M. Libel, Communicable Diseases Program (HCP/HCT)


Direct telephone 001 202 974 31 29
Fax 001 202 974 36 88

Dr. R. Rodriguez, Communicable Diseases Program (HCP/HCT)


Direct Telephone 001 202 974 34 94
Fax 001 202 974 36 88

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

Communicable Diseases Prevention and Control (CDP)


E-mail: moncayoa@who.ch / Surveillancekit@who.ch
Tel: (41 22) 791 3865/3903/2111
Fax: (41 22) 791 4854/0746 attn CRD
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