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September 5, 2025

Chagas disease screening and treatment recommendations in King County

Situation summary

Chagas disease, caused by the parasite Trypanosoma cruzi, can lead to chronic cardiac and gastrointestinal complications, adverse pregnancy outcomes, and congenital Chagas disease if left untreated.

The Washington State Department of Health estimates over 300,000 residents meet screening criteria, yet only an estimated 0.02–0.03% have been screened. An estimated 2,500 Washington residents may be living with undiagnosed and untreated infections, potentially leading to 21–56 preventable congenital cases every decade.

Because most people are unaware they're infected, proactive provider screening and treatment can be lifesaving.

Actions requested

➜ This health advisory is also available in PDF format (306 KB).

  • Screen patients for Chagas disease if they meet any of the following criteria:
    • Born in Mexico, continental Central America, or continental South America, or lived in these areas for 6 months or longer. Of particular concern are those who are:
      • Pregnant and/or
      • Immunocompromised
    • Family members of people diagnosed with Chagas disease who share travel or residence exposure.
    • People whose gestational parents were diagnosed with Chagas disease.
  • Be aware that testing is different for the acute and chronic phases of Chagas disease. In Washington State, most cases are expected to be chronic due to the absence of the insect vector that spreads T. cruzi except for acute Chagas disease considerations below:
    • Acute Chagas disease is diagnosed by blood smear microscopy or polymerase-chain reaction (PCR) testing.
    • Chronic Chagas disease is diagnosed by serologic testing for T. cruzi antibodies.
      • Order a T. cruzi serologic test via a commercial lab for all patients with suspected chronic Chagas disease and who meet screening criteria above.
  • Always order confirmatory serologic testing to confirm the diagnosis of Chagas disease if the initial T. cruzi screening serology is positive.
    • No single serologic test is sensitive and specific enough to diagnose Chagas disease. At least 2 different serologic tests are recommended.
    • Many larger commercial labs, including Mayo Clinic and Quest Diagnostics offer confirmatory testing.
      • Be aware that usually one serum sample can be used for multiple serologic tests.
      • Ask your commercial lab whether positive screening serology automatically reflexes to a second confirmatory test, or if the confirmatory test needs to be coordinated through public health.
      • If your lab does not offer confirmatory testing, contact public health at 206-296-4774 for instructions on how to forward the specimen for confirmatory testing.
  • Ensure screening for cardiac and gastrointestinal complications in patients diagnosed with Chagas disease to assess for treatment.
    • Patients diagnosed with Chagas disease are recommended to receive:
      • Electrocardiogram (ECG) repeated annually.
      • Echocardiogram.
      • Chest x-ray, if an echocardiogram is not possible.
  • Review CDC's clinical care of Chagas disease treatment guidance:
    • Antiparasitic treatment is indicated for all cases of acute or reactivated Chagas disease and all chronic infections in children younger than 18 years.
    • Antiparasitic treatment is strongly recommended for adults up to 50 years old with chronic infection without advanced cardiomyopathy.
    • For adults older than 50 years with chronic infection, the decision to treat should be individualized. See CDC's clinical care of Chagas disease for more details.
    • Antiparasitic treatment is not indicated for people who are pregnant or breastfeeding and should be delayed until after birth or cessation of breastfeeding.
  • Report cases of Chagas disease to Public Health at 206-296-4774 or 206-296-4803 (fax) within 3 business days.

Background

Chagas disease is caused by the parasite Trypanosoma cruzi, primarily transmitted through the feces of infected triatomine bugs (“kissing bugs”). The parasite is mainly found in rural areas of Mexico, Central, and South America. Because Triatomine bugs are not endemic to Washington, most cases diagnosed here are among people born in Latin America or their children.

Early diagnosis and treatment can be lifesaving. In the United States, it is important to recognize infections and prevent its spread through blood transfusion, organ transplants, and from pregnant women to their babies.

Resources

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