Researchers urge U.S. designation of Chagas disease as endemic after cases found in eight states

A study published in the Centers for Disease Control and Prevention journal Emerging Infectious Diseases recommends that Chagas disease — a parasitic infection often described as a “silent killer” — be classified as endemic in the United States after human cases were confirmed in eight states, researchers said.

The authors said acknowledging endemicity is essential for strengthening surveillance, diagnosis and care, and for meeting international health goals. The CDC defines a disease as "endemic" when there is a "constant presence and/or usual prevalence" of a condition within a geographic area.

Chagas disease, also called American trypanosomiasis, is caused by the parasite Trypanosoma cruzi and is transmitted to humans most commonly by triatomine insects, sometimes referred to as "kissing bugs." Infections can cause an acute illness that is frequently mild or asymptomatic and, in some people, progress years later to chronic conditions affecting the heart and gastrointestinal system.

The Emerging Infectious Diseases study reported confirmed human infections across eight states, with a concentration of cases in California. Based on those findings and on evidence of local transmission, the researchers recommended that U.S. public health authorities classify Chagas disease as endemic rather than solely imported.

"Acknowledging the endemicity of Chagas disease in the United States is crucial for achieving global health goals," the study authors wrote, arguing that formal recognition would prompt more targeted surveillance, clinician awareness, and allocation of public health resources.

Public health experts say the designation has practical implications. Recognizing local transmission can expand routine screening efforts, improve detection of chronically infected people who may benefit from antiparasitic treatment, and bolster vector-control measures. Blood-donor screening and some clinical testing have identified infections in the United States in prior years, but researchers and clinicians have warned that underdiagnosis remains a problem because symptoms are often nonspecific and infections may remain asymptomatic for years.

Diagnosis typically relies on laboratory testing for the parasite or for antibodies produced in response to infection. Antiparasitic medications such as benznidazole and nifurtimox are used to treat Chagas disease; treatment is most effective in the early stages of infection and may reduce the risk of long-term complications when given promptly.

Triatomine insects capable of carrying T. cruzi are known to occur in parts of the southern United States, and previous studies have documented infected animals and insect vectors in multiple regions. The new study’s authors said their findings of confirmed human infections, including cases without recent travel to endemic countries, support the view that local transmission is occurring and that the baseline risk within some U.S. communities is higher than previously recognized.

Health officials and researchers have emphasized that raising clinician awareness is a near-term priority. Symptoms of chronic Chagas-related cardiomyopathy include heart rhythm abnormalities, heart failure and an increased risk of stroke; gastrointestinal manifestations can include enlargement of the esophagus or colon. Because many infected people do not recall an acute illness, clinicians must consider exposure risk and testing when unexplained cardiac or gastrointestinal disease arises.

The study’s recommendation for endemic classification aligns with broader global efforts to better detect and manage neglected parasitic infections. The authors noted that recognition at the national level would facilitate public health planning, improve access to diagnostic testing and treatment, and help guide community-level interventions to reduce vector exposure.

The CDC did not immediately adopt the study’s recommendation; classification decisions typically involve review of epidemiologic data and consultation with state and federal partners. Meanwhile, researchers called for expanded surveillance, increased clinician education, and continued investigation into the geographic distribution of infected vectors and human cases.

Recognizing Chagas disease as endemic in parts of the United States would not change the nature of the parasite or its transmission, but public health advocates say it could sharpen detection efforts, reduce missed diagnoses, and open channels for targeted prevention and treatment services for affected communities.