Food inspection officials are concerned that some of the products sold at Trader Joe's, Kroger and Walgreens may still be in home refrigerators and have urged consumers to throw them out or return them to stores.
Consumers may have already ingested the parasite, and it may be incubating without producing symptoms, the USDA said. The agency provided a list of products by name and UPC code but not specific locations.
The Cyclospora cayetanensis parasite can cause illness that is not life-threatening, with symptoms such as diarrhea, vomiting and fever, the Centers for Disease Control and Prevention warns.
It is the same parasite responsible for a nationwide outbreak linked to McDonald's salads last month, causing at least 286 confirmed illnesses in 11 states, the CDC said. The outbreak triggered recalls at thousands of stores.
The romaine lettuce used in some of the products in this new warning came from Fresh Express, which was linked to the McDonald's outbreak.
Fresh Express could not be reached for comment.
The outer limit of the incubation period for this batch of food is Aug. 6, the USDA said, and it could be up to six weeks before officials begin to receive reports of illness.
The USDA did not respond to a request for comment. It is not clear whether any illnesses have been reported from ingesting products linked to the newest warning.
FDA Commissioner Scott Gottlieb said Wednesday that the positive samples from recalled McDonald's salad were confirmed using a new method that helps the agency investigate and identify the Cyclospora parasite.
There has been a cascade of food-borne illnesses across the United States this year. The USDA on Wednesday warned about potential salmonella contamination in some products that use whey, including certain Ritz crackers and Goldfish products.
Romaine lettuce was determined to be contaminated with E. coli. Fresh crab meat from Venezuela was deemed a risk after Vibrio parahaemolyticus sickened a dozen people in three states and Washington.
The uptick may be a combination of more incidents and better detection methods, food safety lawyer Bill Marler told The Post.
Lindsey Bever contributed to this report.