Is Chagas disease present in the United States?

Yes. The triatomine bug that transmits Chagas is found in the southern United States, and an estimated 100,000 or more immigrants from endemic regions may be infected. The U.S. began screening donated blood for Chagas in 2007 due to these concerns.

How does Chagas disease spread through blood transfusion?

The Trypanosoma cruzi parasite lives in blood. When infected blood is transfused without screening, the parasite can establish infection in the recipient. This is a known risk in endemic countries and became a concern in the U.S. as immigration from Latin America increased.

What are the symptoms of Chagas disease?

The acute phase (first few weeks) affects only about 1% of people with noticeable symptoms — including eye swelling (Romaña's sign), fever, fatigue, and body aches. Most then enter a long silent phase. Chronic disease emerges 10–20 years later in 20–30% of infected people, causing serious heart or digestive complications.

Can Chagas disease be treated?

Yes, but only during the acute phase. Two drugs — benznidazole and nifurtimox — can cure infection when given early. In the chronic phase, treatment can slow progression but cannot reverse established heart or organ damage.

Chagas Disease: Transmission, Stages, and Blood Supply Risk

Chagas disease is a parasitic infection that has long been a major public health concern in Latin America — and is now recognized as an emerging threat to blood supply safety in the United States. Understanding how it spreads, what it does to the body, and why it matters for the blood supply is increasingly important as global migration patterns shift.

What Is Chagas Disease?

Chagas disease is caused by the protozoan parasite Trypanosoma cruzi, first identified by Brazilian physician Carlos Chagas in 1909. It infects an estimated 18 million people worldwide and kills approximately 50,000 people annually — numbers that place it among the most deadly parasitic diseases in the Western Hemisphere.

The disease is endemic to Central and South America, where it has historically been a major cause of heart disease. As immigration from endemic regions has grown, Chagas has become a recognized concern in the United States, Europe, and other non-endemic regions where blood screening programs were not originally designed for it.

How Is Chagas Disease Transmitted?

The Kissing Bug

The primary vector is the triatomine insect — commonly called the “kissing bug” or reduviid — which feeds on blood at night, typically biting near the eyes or mouth while a person sleeps. The bug deposits feces containing T. cruzi near the bite wound. When the person scratches the area, the parasite enters through broken skin or mucous membranes.

This route accounts for the majority of Chagas infections in endemic areas, where housing conditions allow the bugs to live in walls and thatched roofs. Triatomine bugs are also present in the southern United States, raising the possibility of local transmission.

Other Transmission Routes

Chagas disease can also spread through:

Blood transfusion: The parasite survives in stored blood and can infect recipients if the donation is not screened
Organ transplant: Recipients of organs from infected donors are at risk
Vertical transmission: An infected mother can pass T. cruzi to her child during pregnancy, childbirth, or breastfeeding
Contaminated food: Consuming uncooked or unprocessed food contaminated with infected bug feces (oral transmission)
Laboratory accidents: Rare occupational exposure among researchers working with the parasite

What Are the Stages of Chagas Disease?

Acute Phase

The acute phase begins within days of infection and lasts several weeks. Remarkably, only about 1% of infected people develop noticeable symptoms during this stage. When symptoms do occur, they may include:

Romaña’s sign: Painless swelling of one eyelid, a hallmark of Chagas when the parasite enters through the eye area
Fever and fatigue
Body aches and headache
Swelling at the bite site (chagoma)
Enlarged lymph nodes, liver, or spleen

In young children, the acute phase can be severe — potentially causing fatal brain inflammation (meningoencephalitis) or heart inflammation (myocarditis). Adults rarely die from the acute phase.

Indeterminate (Silent) Phase

Eight to ten weeks after acute infection, most people enter an indeterminate phase where the immune system controls parasite levels and no symptoms are apparent. Infected individuals may remain in this stage for years or decades — or for life — without ever developing further complications.

However, they remain capable of transmitting the parasite through blood donation, organ transplant, or to a developing fetus.

Chronic Phase

After 10–20 years, approximately 20–30% of people with Chagas infection develop serious chronic complications. The chronic phase manifests in two primary forms:

Cardiac Chagas disease: The most dangerous form, causing progressive damage to the heart muscle (cardiomyopathy). The heart enlarges, the electrical conduction system becomes disrupted, and the risk of sudden cardiac death rises dramatically. Heart failure can develop even in previously asymptomatic individuals in their 30s, 40s, or 50s.

Digestive Chagas disease: The parasite destroys nerve cells in the digestive tract, causing megaesophagus (severe swallowing difficulties) or megacolon (massive colonic enlargement with constipation). These complications are debilitating and can be life-threatening.

Once chronic damage is established, it cannot be reversed. Treatment shifts to managing symptoms and complications.

Why Is Chagas a Blood Supply Risk?

The Immigration Factor

An estimated 100,000 immigrants from Chagas-endemic regions currently live in the United States and may unknowingly carry T. cruzi. Many are asymptomatic and in the long silent phase. Without targeted screening, they can donate blood that tests negative for all standard pathogens — while carrying a potentially transmissible parasite.

The 1996 U.S. Congressional report on blood supply safety identified Chagas disease as a growing concern requiring attention, specifically because of increased immigration from Central and South America.

Blood Transfusion Transmission

Trypanosoma cruzi survives in refrigerated blood for weeks. In countries where Chagas is endemic and blood screening is limited, transfusion-transmitted Chagas is a documented problem. The United States began screening donated blood for Chagas antibodies in 2007 using an FDA-approved test developed by Ortho Clinical Diagnostics.

Since screening began, hundreds of infected donors have been identified in the U.S., with a concentration in states with large Latin American immigrant populations including California, Texas, and Florida.

The Cost of Screening

Blood screening for Chagas costs approximately $1–$5 per unit. Across roughly 14 million annual donations in the United States, comprehensive screening represents a meaningful but manageable cost — and one generally considered justified given the severity of chronic Chagas disease and the lack of any other treatment option once infection is established.

Is There a Treatment or Vaccine?

No vaccine exists for Chagas disease. The two available medications — benznidazole and nifurtimox — are effective if treatment begins during the acute phase. When treatment is initiated promptly, cure rates are high.

In the chronic phase, these drugs may slow disease progression or reduce parasite burden, but they cannot reverse established cardiac or digestive damage. Management of chronic Chagas focuses on treating the complications: heart failure medications, antiarrhythmics, pacemakers, or surgical interventions for digestive complications.

What Should You Do If You’re at Risk?

If you or a family member immigrated from or spent significant time in Central or South America — particularly in rural areas — and have never been tested for Chagas, testing is advisable. Antibody blood tests can detect T. cruzi infection. Testing is especially important before donating blood, becoming pregnant, or if cardiac symptoms develop.

For context on broader blood supply safety measures and how infections like Chagas factor into regulatory oversight, see FDA blood safety regulations and the blood supply safety overview.