Chagas disease
2025 Case Definition
2025 Case Definition
CSTE Position Statement(s)
24-ID-04
Subtype(s)
- Chagas disease, acute
- Chagas disease, chronic
- Chagas disease, congenital
Background
Chagas disease is an infection caused by the protozoan parasite Tyrpanosoma cruzi. Infection with T. cruzi has been well-characterized in Latin America, where it is primarily transmitted by triatomine vectors. While imported cases of Chagas disease outnumber locally-transmitted cases, enzootic transmission of T. cruzi has been described in the United States (U.S.), where there are 11 triatomine vectors. In addition to vector-borne transmission, Chagas disease has been domestically observed to transmit via blood transfusion, organ transplantation, and vertically from a gestational parent to their fetus. While many infections with T. cruzi are mild, chronic infection can result in significant pathology and progression to severe and fatal disease.
Different testing methods are needed to diagnose Chagas disease depending on the phase of the infection. Microscopy and molecular tests are employed in the acute phase of Chagas disease or in the event of suspected reactivation. Serologic testing for host immunoglobulin G (IgG) against T. cruzi antigens is the preferred method for diagnosing chronic Chagas disease. Serologic testing is also used in the context of screening donors of blood, organs, and human cells, tissues, and tissue-based products (HCT/P). Importantly, the sensitivities and specificities of the currently available assays are not high enough for a single assay to be used alone.
Many T. cruzi infections go unrecognized. This is likely due to the progression from acute to chronic indeterminate Chagas disease one to two months after initial infection, during which parasitemia falls below levels commonly detectable by microscopy and the host becomes asymptomatic, as well as lack of familiarity with the disease among clinicians.
Without appropriate treatment, infection with T. cruzi lasts for the life of the host due to the parasite’s replication cycle. Approximately 20-30% of infected individuals go on to develop Chagas cardiomyopathy or gastrointestinal disease. Immunocompromised individuals are at particularly high risk of severe Chagas disease reactivation. In some of these cases, Chagas disease has involved the central nervous system, exacting a high case fatality rate. (Hochberg & Montgomery, 2023; Forsyth et al., 2022)
Criteria to Distinguish a New Case from an Existing Case
A person should not be enumerated as a case of Chagas disease more than once within the same case category (e.g., a person previously enumerated as a case of acute Chagas MAY be enumerated as a case of chronic Chagas, but MAY NOT be enumerated as a case of acute Chagas for a second time).
Subtype(s) Case Definition
Laboratory Criteria
Confirmatory Laboratory Evidence:*, **
- Visualization of T. cruzi by microscopy (e.g. wet mount-microscopic examination, thick and thin smears-Giemsa stain) performed on any tissue or body fluid
OR
- Detection of T. cruzi DNA by molecular testing (e.g. NAAT, metagenomic sequencing) performed on any tissue or body fluid.
Note: The categorical labels used here to stratify laboratory evidence are intended to support the standardization of case classifications for public health surveillance. The categorical labels should not be used to interpret the utility or validity of any laboratory test methodology.
* Individuals experiencing reactivation may test positive using molecular testing or microscopic observation. These individuals can be counted as a chronic case pending positive serology that meets the chronic case definition. In the context of transplant recipients, case classification should be informed by whether the positive result may reflect an acute, donor-derived infection or chronic infection in a case experiencing reactivation.
** See Appendix 1 for more information related to signs and syndromes of acute and congenital Chagas disease 
.
Epidemiologic Linkage
- Suspected triatomine or kissing bug exposure (e.g., bite, triatomine found in bed, etc.) within the 3 months prior to specimen collection,
OR - Residence for at least 6 months in a Chagas endemic country¥, which concluded within the 3 months prior to specimen collection,
OR - History of donor-derived infection in the recipient of organ or HCT/P transplant within the 3 months prior to specimen collection,
OR - History of donor-derived infection in the recipient of a blood transfusion within the 3 months prior to specimen collection.
¥ Argentina, Belize, Bolivia, Brazil, Chile, Colombia, Costa Rica, Ecuador, El Salvador, French Guiana, Guatemala, Guyana, Honduras, Mexico, Nicaragua, Panama, Paraguay, Peru, Suriname, Uruguay, and Venezuela.
Case Classification
Confirmed
- Meets acute Chagas disease confirmatory laboratory evidence AND acute Chagas disease epidemiologic linkage criteria.**
** See Appendix 1 for more information related to signs and syndromes of acute and congenital Chagas disease .
Laboratory Criteria
Confirmatory Laboratory Evidence:‡
- Detection of IgG antibodies specific to T. cruzi by at least two diagnostic tests using two different
antigen preparations.^
Presumptive Laboratory Evidence:‡
- Detection of IgG antibodies specific to T. cruzi by a single diagnostic test,
OR
- Positive blood, organ, or HCT/P donor screen for T. cruzi.^^
Note: The categorical labels used here to stratify laboratory evidence are intended to support the standardization of case classifications for public health surveillance. The categorical labels should not be used to interpret the utility or validity of any laboratory test methodology.
^ See Appendix 3 for more information related to antigen preparations for T. cruzi-specific IgG tests .
^^ Blood, organ, and HCT/P donor screening does not constitute diagnostic testing.
‡ Includes chronic indeterminate and chronic symptomatic Chagas disease. See Appendix 2 for more information related to chronic Chagas disease .
Epidemiologic Linkage
- Gestational parent that delivered a fetus or infant with confirmed congenital T. cruzi infection.
Case Classification
Suspect
- Meets only one chronic Chagas disease presumptive laboratory evidence criterion.‡
Probable
- Meets all chronic Chagas disease presumptive laboratory evidence criteria,‡
OR
- Meets one chronic Chagas disease presumptive laboratory evidence criterion AND chronic Chagas disease epidemiologic linkage criterion.‡
Confirmed
- Meets chronic Chagas disease confirmatory laboratory evidence.‡
‡ Includes chronic indeterminate and chronic symptomatic Chagas disease. See Appendix 2 for more information related to chronic Chagas disease .
Laboratory Criteria
Confirmatory Chagas Disease:**, ***
- Visualization of T. cruzi by microscopy (e.g., wet mount-microscopic examination, thick and thin smears-Giemsa stain) performed on any tissue or body fluid (collected from the fetus or infant within three months of delivery to gestational parent),
OR
- Detection of T. cruzi DNA by molecular testing (e.g., NAAT, metagenomic sequencing) performed on any tissue or body fluid (collected from the fetus or infant within three months of delivery to gestational parent).
Note: The categorical labels used here to stratify laboratory evidence are intended to support the standardization of case classifications for public health surveillance. The categorical labels should not be used to interpret the utility or validity of any laboratory test methodology.
** See Appendix 1 for more information related to signs and syndromes of acute and congenital Chagas disease .
*** Individuals experiencing reactivation may test positive using molecular testing or microscopic observation. These individuals can be counted as a chronic case pending positive serology that meets the chronic case definition. In the context of transplant recipients, case classification should be informed by whether the positive result may reflect an acute, donor-derived infection or chronic infection in a case experiencing reactivation.
Case Classification
Confirmed
A fetus (≥20 weeks or ≥350g) or an infant who meets congenital Chagas disease confirmatory laboratory evidence in the absence of other known routes of transmission.**
** See Appendix 1 for more information related to signs and syndromes of acute and congenital Chagas disease .
References
- Hochberg, N. S., & Montgomery, S. P. (2023). Chagas disease. Annals of Internal Medicine, 176(2), ITC17-ITC32. https://doi.org/10.7326/AITC202302210
- Forsyth, C. J., Manne-Goehler, J., Bern, C., et al. (2022). Recommendations for screening and diagnosis of Chagas disease in the United States. Journal of Infectious Diseases, 225(9), 1601-1610. https://doi.org/10.1093/infdis/jiab513