San Diego confirms first local Chagas infection. Expert says ‘be smart’

For the first time, an individual in San Diego County has tested positive for Chagas disease after acquiring the parasitic infection locally.

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The case was identified through a routine blood donation screening in a donor who exhibited no symptoms, county spokesperson Fernanda Lopez Halvorson said in a Monday news release. 

Chagas disease is caused by the parasite Trypanosoma cruzi and is typically spread when parasite-laden feces from an infected insect called a triatomine — commonly known as a kissing bug — enter the bite wound after the insect feeds. The disease is more common in Latin America, but it has increasingly been found in California in recent years. 

The species that carries the parasite in California is different than those found in Latin America, and it typically lives in rodent nests rather than homes, making camping and other outdoor exposure potential risk factors. 

Dr. Peter Chin-Hong, an infectious disease expert at UC San Francisco, told SFGATE that the San Diego County case does not mean Californians should panic. Unlike in parts of Latin America, where some kissing bugs live inside homes and frequently feed on sleeping people, California’s kissing bugs are more commonly associated with wood rat nests. 

“California infection is so rare,” Chin-Hong said. “Humans actually have to go into the woods and interact with these nests. People shouldn’t panic about going into the woods, but it’s kind of like the whole hantavirus thing. You want to be smart.”

He said local transmission remains uncommon for another reason. Globally, the most common kissing bugs defecate while biting the host, allowing parasites to enter the bite. However, in California, these insects usually leave the host before defecating, reducing the chance that parasite-carrying feces will be rubbed into the bite. 

Blood donation screening has helped identify people who did not know they were infected, Chin-Hong noted, because many remain symptom-free for years. 

Since San Diego County made Chagas disease locally reportable in 2024, health officials have received 22 reports and confirmed four cases, including this case, which is the region’s first known locally acquired infection. 

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“Identifying a locally acquired Chagas case reminds us that this disease is not limited to Latin America,” Dr. Sayone Thihalolipavan, San Diego County’s public health officer, said in a statement.

A 2025 review affiliated with the U.S. Centers for Disease Control and Prevention advised that Chagas is becoming more common in the U.S. and should no longer be treated as only a foreign or travel-related disease. Researchers noted that kissing bugs have been found in 32 states, locally acquired human cases have been identified in seven states, and California’s San Diego and Los Angeles counties now require local reporting. 

Early Chagas infection often causes no symptoms or a mild flu-like illness, including fever, headache, cough, abdominal pain or swelling at the bite site. Years or decades later, about 30% to 40% of infected people may develop serious heart or gastrointestinal complications. 

Chin-Hong said heart complications are the primary concern. Some patients can develop heart failure, arrhythmias or electrical conduction problems in the heart years after infection. 

To reduce the risk of exposure, Chin-Hong recommended avoiding contact with rodents and rodent nests, sealing cracks or gaps around homes, and controlling rodent infestations. If people find kissing bugs indoors, he said, they should avoid handling them and consider having them identified by public health officials. Those who test positive for the disease can take antiparasitic drugs or receive supportive care if the disease has progressed enough to cause complications, according to the CDC.