Chagas disease, also called American trypanosomiasis, is an infection caused by a single-celled parasite. It spreads through the feces of infected triatomine bugs, also known as kissing bugs. Infections are most common in rural parts of Mexico and Central and South America, but also occur in many other countries, including the United States.

The illness has two stages. The early stage (acute phase) often causes mild or no symptoms. The long-term stage (chronic phase) can lead to serious heart and digestive system problems many years or decades later. Early diagnosis and treatment can save lives.

About 8 million people worldwide are estimated to be infected. In the United States, an estimated 280,000 people have Chagas disease, although many are unaware they are infected.

Chagas disease is an infection caused by the parasite Trypanosoma cruzi (T. cruzi). Kissing bugs, which feed on animal or human blood, can carry this parasite. After feeding, the bugs often defecate close to the bite. People get infected when the bug droppings, which can harbor the parasite, get into their body through the bite wound, the eye, the mouth, or a break in the skin. Once infected, a person can carry the parasite in their body for decades.

Chagas disease has two clinical stages:

• Acute phase: In the first weeks or months after infection, people may experience mild, flu-like symptoms, although some have no symptoms.
• Chronic phase: In this phase, the parasite continues to live in the heart or digestive muscles. Many infected people have no symptoms for years, while others eventually develop heart or digestive disease.

Chagas disease results from an infection with the T. cruzi parasite. People can become infected in several ways:

• Coming into contact with feces from the kissing bug (parasites in the feces enter through a break in the skin, or in the eyes or mouth)
• Being born to an infected mother
• Receiving a transfusion of blood or blood products from an infected donor
• Receiving a transplanted organ from an infected donor
• Eating or drinking items contaminated with infected bug feces
• Accidental exposure in a laboratory

Chagas disease is not transmitted through the air or by everyday contact with infected people or animals.

Certain factors raise the risk of infection with a T. cruzi parasite, including the following:

• Living in or traveling to rural parts of Mexico and Central or South America or other areas where kissing bugs live
• Sleeping in at-risk areas either outdoors or in buildings that do not have screens or air conditioning or have cracks in the wall or roof
• Having a family member with Chagas disease and sharing similar exposures, such as living in the same at-risk rural area
• Being born to a mother with Chagas disease
• Receiving a blood transfusion or an organ transplant from an infected donor
• Eating raw produce, unpeeled fruits, or unpasteurized juices in locations with an active outbreak
• Working with the parasite in a laboratory

Kissing bugs live both indoors and outdoors. Inside, they may be found in cracks and crevices in the roof and in the walls. Outside, they may be found under porches; in wood, brush, or rock piles; in animal burrows; in outdoor dog kennels; and in chicken coops. In the United States, kissing bugs are most often found in the South. Homes there are usually tightly built, so indoor infestations are uncommon.

Symptoms vary by stage, though many people have no symptoms.

Acute phase (first weeks or months after infection) symptoms may include:

• Fever
• Unusual tiredness
• Body aches or headache
• Rash
• Loss of appetite
• Diarrhea or vomiting
• Swelling of one eyelid (Romaña’s sign) when parasites enter through the eye
• A small, firm skin sore at the entry site (chagoma)
• Swollen lymph nodes
• Enlarged liver or spleen
• Trouble breathing, chest pain, or belly pain

Chronic phase (years or decades later) symptoms may include:

Most people remain symptom-free for many years after infection. However, some people develop serious heart or digestive problems. These delayed symptoms can include:

• Irregular heartbeat (arrhythmia), or a slow or fast heart rate
• Enlarged or damaged heart
• Heart failure
• Sudden death
• Blood clots that can lead to stroke
• Enlarged esophagus, which can lead to trouble swallowing, regurgitation, cough, and weight loss
• Enlarged colon, which can cause long-lasting constipation and belly pain

To diagnose Chagas disease, the doctor will usually review your medical history, conduct a physical exam, and order one or more diagnostic tests.

The doctor may ask about your symptoms and where you have lived or traveled. They may ask about possible kissing bug exposure, blood transfusions, organ transplants, or whether your mother could have had the infection. They may also ask about eating or drinking items that could have been contaminated in areas where the disease is common.

During the physical exam, the doctor will check for fever, swollen lymph nodes, and an enlarged liver or spleen. They will look for swelling of one eyelid or a small, firm skin sore. They may check your pulse and listen for an irregular heartbeat.

Additional tests are necessary to confirm a diagnosis. These may include:

• Blood smear: This test examines blood under a microscope to look for the parasite. It is used during the acute infection phase, or in newborns.
• Polymerase chain reaction (PCR): This kind of test can detect the parasite’s genetic material in blood.
• Blood tests for antibodies, such as enzyme-linked immunosorbent assay (ELISA): Testing for antibodies can confirm a chronic infection.
• Blood culture: This test looks for signs of infection in the blood.
• Electrocardiogram (ECG): This records the heart’s electrical activity to check for abnormal patterns.
• Echocardiogram: This test uses sound waves to evaluate the heart’s structure and pumping function.
• Chest X-ray: An X-ray can check the size and shape of the heart and blood vessels in the chest.

Treatment for Chagas disease aims to kill the parasites and ease symptoms.

Antiparasitic medicines can kill the parasite. They are most effective when they are started early. In the United States, two medicines are available, benznidazole and nifurtimox. A health care provider may consult experts to select the best option. Potential benefits are usually weighed against the possible side effects and length of the treatment, which can take up to two months. Most people can receive this treatment without being admitted to the hospital. Doctors may prescribe antiparasitic treatment for:

• People diagnosed during the acute phase
• Babies who are born with a T. cruzi infection
• Individuals who are immunocompromised who have newly recurring symptoms
• People with chronic (long-standing) Chagas infection, including some without symptoms, to reduce the chance of disease progression

Side effects are more common in older adults. These can include:

• Headaches or dizziness
• Loss of appetite and weight loss
• Skin rashes
• Sleep problems
• Tingling, numbness, or other nerve problems

Pregnant people and people with severe kidney or liver disease should not take benznidazole or nifurtimox. Nifurtimox is also not recommended for people with certain neurological or psychiatric conditions.

Other treatments can address symptoms of chronic Chagas disease, which can cause severe heart, digestive tract, or nervous system problems. A doctor may refer a patient to cardiology, gastroenterology, or infectious disease specialists for care. Treatments for symptoms may include heart care for arrhythmias, heart failure, or blood clots, including devices such as pacemakers. People may also be treated for swallowing problems or severe constipation. Regular checkups are recommended to monitor a person’s health and treat any new symptoms.

Possible complications include:

• Irregular heartbeat, fainting, or dizziness
• Enlarged heart and heart failure
• Blood clots and stroke
• Sudden death
• Enlarged esophagus with swallowing difficulty, regurgitation, cough, and weight loss
• Enlarged colon with severe constipation and belly pain
• Malnutrition related to long-standing eating and swallowing problems
• Reactivation with severe illness in people who have a compromised immune system

There are no vaccines or preventive medicines for Chagas disease. The best ways to prevent Chagas disease are to avoid contact with kissing bugs and block other transmission routes.

When living in or traveling to areas at risk:

• Look for lodging with solid construction and screens or air conditioning. Kissing bugs can more easily get into poorly built dwellings.
• While sleeping, use bed nets treated with long-lasting insecticide to help prevent bites from kissing bugs.
• Wear long sleeves and long pants outdoors, and apply insect repellent to exposed skin.
• Treat sleeping areas with long-lasting insecticides.
• In at-risk areas, do not eat salads or raw vegetables. Peel fruit before eating and drink only pasteurized fruit juices. General preventive measures outside of areas where kissing bugs are constantly present (endemic):
• Seal cracks and gaps around windows, doors, walls, roofs, and foundations.
• Install and repair window and door screens.
• Keep the area around the home free of wood, brush, and rock piles.
• Position outdoor lights away from the house as bugs can be attracted to light.
• Seal openings to attics and crawl spaces.
• Keep pets inside when they sleep, in particular at night.
• Clean pet resting areas regularly and watch for bugs.
• Consult a pest control expert before using insecticides. (There are no products approved for eliminating kissing bugs in the United States.)

The following measures reduce the spread of this infection from blood donations, organ donations, or from mother to child:

• Blood centers in continental Latin America and the United States screen donations to lower transfusion risk.
• Transplant programs test organs before transplant.
• Testing and treating women of reproductive age, newborns, and siblings can help detect infections and prevent transmission. Antiparasitic medicines can also lower the chance of a woman passing the infection to a developing baby in future pregnancies.
• Most mothers with Chagas disease can breastfeed safely. However, if nipples become cracked or there is blood in breast milk, mothers should pump and discard milk until healed.
• In addition, community and public health strategies can help prevent Chagas disease. Solidly built housing and long-lasting insecticides in at-risk communities help reduce indoor bug infestations.
• Early access to diagnosis, antiparasitic treatment, and lifelong follow-up improve health outcomes and reduce spread of the disease.
• Information and education for communities and health professionals helps support prevention and care.

The outlook depends on the stage of disease at diagnosis and the availability of effective treatment. In the acute phase of the disease, most people have mild symptoms that improve on their own. When started early, antiparasitic medicines can cure the disease, including in babies who were infected in the womb.

Many people with a chronic infection never develop symptoms. However, without early diagnosis and treatment, up to one in three people with a chronic infection develop digestive problems, heart disease, or both.

Treatment and follow-up care can change the course of the disease. In chronic infection, antiparasitic medicine can prevent or slow down disease progression. Symptom-based heart and digestive care can improve quality of life. Regular checkups help detect health changes early, when they are easier to manage.

Because Chagas disease often remains silent for years, testing people at risk is essential. Early diagnosis and treatment can greatly improve health outcomes and save lives.

“Due to increased population mobility over recent decades, coupled with the expansion of the insect vector’s habitat as a consequence of climate change, Chagas disease has emerged as an important public health concern beyond endemic regions,” says Yale Medicine cardiologist and internal medicine specialist Bernardo Lombo, MD, director of the Chagas Disease Alliance at Yale (CDAY). “It now significantly affects Latin American diaspora communities and populations in the southern United States, with substantial social and economic impact.”

In response to this growing challenge, Yale established CDAY. “CDAY is a multidisciplinary network of researchers, healthcare providers, and public health professionals dedicated to advancing basic and translational research on Chagas disease, strengthening screening and diagnostic efforts, and delivering comprehensive clinical care to individuals with a confirmed diagnosis. Guided by the principle of ‘thinking globally and acting locally,’ the CDAY engages in ongoing research collaborations, patient care initiatives, policy advocacy, and capacity-building efforts in both New Haven and across Latin America,” says Dr. Lombo.