San Francisco Reports 10 Cases of Cyclospora Parasite Linked to US Outbreak

Public health authorities are tracking a multi-state outbreak of cyclosporiasis, a foodborne illness caused by the parasite Cyclospora cayetanensis, with 145 confirmed cases spanning 20 states between May and June 16, according to the Centers for Disease Control and Prevention. The infection, which leads to severe watery diarrhea, cramping, and fatigue, has resulted in 20 hospitalizations across the country, though no deaths have been reported.

Multi-State Distribution and Case Numbers

Patients ranging in age from 5 to 86 years old have contracted the parasite, according to federal health data. New York has recorded the highest number of infections in the country, with between 31 and 80 cases. Texas and Illinois follow as the next most-impacted areas, each logging between 11 and 30 cases, according to reporting by the New York Post.

Additional cases have been confirmed in New Jersey, Connecticut, Pennsylvania, Massachusetts, Rhode Island, Delaware, Maryland, Virginia, North Carolina, Ohio, Tennessee, Wisconsin, Georgia, Florida, Louisiana, Colorado, Alaska, and Washington, D.C., along with 10 confirmed cases in San Francisco, according to the San Francisco Chronicle and the Centers for Disease Control and Prevention. Because many individuals with mild symptoms may not seek medical care or receive a formal diagnosis, public health officials note that the true case count is likely higher than official tallies indicate.

Symptoms and Medical Treatment

Cyclosporiasis is a type of food poisoning that primarily affects the small intestine. Symptoms typically develop about a week after a person ingests the parasite. The hallmark sign is explosive, watery diarrhea, accompanied by other gastrointestinal distress such as severe cramping, nausea, vomiting, bloating, low-grade fever, fatigue, and a loss of appetite.

While some infections can resolve without medical intervention, untreated cases can cause symptoms to persist for a month or longer, significantly increasing the risk of dehydration. When diagnosed, the infection is typically treated with a course of antibiotics, specifically trimethoprim-sulfamethoxazole, which is commonly known by brand names such as Bactrim, Septra, or Cotrim, according to the Centers for Disease Control and Prevention.

Investigation Into Contamination Sources

Investigators at the local, state, and federal levels—including the Centers for Disease Control and Prevention and the Food and Drug Administration—are actively examining several clusters of cases across multiple states to determine how the parasite is spreading. Officials have found no evidence that the infection spreads directly from person to person.

Instead, because none of the affected individuals reported recent travel outside the United States, public health authorities believe the illness is linked to domestically consumed food. Cyclosporiasis is traditionally associated with travel to tropical or subtropical regions where contaminated food or water is ingested, but the current domestic clusters point toward imported or distributed food supplies within the country.

Previous United States outbreaks of the parasite have frequently been tied to fresh, imported produce. Past investigations implicated items such as cilantro, raspberries, sweet peas, mesclun lettuce, and basil imported from Mexico during a 2019 outbreak, as well as tainted salads at McDonald’s locations that sickened nearly 400 people in 2018. Federal agencies continue their ongoing traceback investigations to pinpoint the specific food vehicle responsible for the current multi-state spread.