Chagas disease or American trypanosomiasis is caused by the parasite Trypanosoma cruzi. It can be transmitted congenitally, orally, and through the bite of an insect vector, most commonly the triatomine bug or kissing bug. The World Health Organization and Pan American Health Organization (PAHO) recognize 21 endemic countries in the Americas, excluding the United States. As a result, the U.S. is frequently described in scientific literature, on the CDC’s website, and by the media as nonendemic. However, compelling evidence of locally acquired human infection, broad vector presence, and continuous sylvatic cycles of T. cruzi strongly support reclassifying the U.S. as endemic.
Triatomines are native to the southern half of the U.S. and are documented in 32 states. Eleven species are present, 9 of which are positive for T. cruzi. Four species, Triatoma sanguisuga, T. gerstaeckeri, T. protracta, and T. rubida, are frequently encountered in homes, increasing the risk for human contact. The infection rate of triatomines in endemic areas ranges between 30% and more than 50%. T. gerstaeckeri is especially associated with transmission in Texas, where cases in both canines and humans have been recognized.
Wildlife also plays a significant role. Infections have been documented in at least 17 southern states among species such as opossums, raccoons, armadillos, woodrats, skunks, and coyotes. Some species have a prevalence greater than 50%. Opossums can transmit parasites through secretions from their anal glands and vertically to their offspring. In the reservoirs of the U.S., discrete typing units I and IV are most frequently identified.
Eight states have reported human cases that were locally acquired: Arkansas, Mississippi, Missouri, Louisiana, Tennessee, Texas, Arizona, and California. Between 2000 and 2018, 29 confirmed cases and 47 suspected cases of locally acquired human Chagas disease were reported, though actual numbers were likely higher. Human Chagas disease is not nationally notifiable but is tracked in 8 states and two countries in California.
Since 2013, Texas has reported 50 locally acquired cases of Chagas disease, representing the highest burden of Chagas in the U.S. This includes three acute cases, 44 were chronic asymptomatic, and 3 were chronic symptomatic cases, with 66% of chronic cases confirmed by CDC testing.
Cases have been reported annually without any evidence of reduction. The first U.S. case was identified in 1955 in Corpus Christi, and parasite DNA was subsequently detected in a 1,150-year-old Texas mummy, suggesting long-standing transmission.
While the prevailing assumption was that the U.S. triatomines transmitted less efficiently, it has been documented that T. sanguisuga and T. gerstaeckeri are capable of fecal defecation during feeding, thus ensuring transmission occurred. It should be noted that documented human cases occurred without any reported insect exposure, and this could indicate oral transmission, as seen in Latin America.
The CDC describes endemicity as the continued or constant existence of a disease in a certain geographic area. WHO further categorizes into hypoendemic, mesoendemic, and hyperendemic. U.S. data confirm stable cycles in wildlife cycles, and persistent human cases align with hypoendemic status.
Labelling the U.S. as nonendemic lowers awareness, causes underdiagnosis, and frames Chagas as a foreign disease. Although the U.S. contributes 23.3% of the world’s research output, much of the focus is on pharmacology and diagnostics rather than surveillance or prevention. If we recognize endemicity, it will promote funding, surveillance, education, and the WHO’s road map for neglected tropical diseases.
The transmission of Trypanosoma cruzi is strongly established in wildlife, domestic animals, and humans in the U.S. With nearly the entire U.S. range of triatomines, high prevalence in domestic dogs and cats, and consistent human cases, evidence supports classifying the U.S. as endemic, specifically hypoendemic. Reclassifying the U.S. would strengthen surveillance, public health measures, and clinical awareness while reframing Chagas disease as a regional, not foreign, health concern.
References: CDC. Chagas Disease, an Endemic Disease in the United States. Published September 9, 2025. Accessed September 9, 2025. Chagas Disease, an Endemic Disease in the United States
