Red onions grown in California have been traced as the potential source of a salmonella outbreak that has infected more than 500 people in the United States and Canada, health officials said.
Confirmed cases have surfaced in 34 states. Those most affected as of Saturday included Oregon (71); Utah (61) and California (49), the Food and Drug Administration said.
The Public Health Agency of Canada reported that the country had 114 cases of salmonella and that at least 16 people had been hospitalized. In the United States, 396 illnesses and 59 hospitalizations have been reported, the F.D.A. said.
The administration said it was able to identify Thomson International, a produce supplier in Bakersfield, Calif., as a likely source of contaminated red onions.
Thomson said on Saturday that it recalled red, yellow, white and sweet onions that were shipped since May 1 because of the risk of contamination.
Onions were distributed to wholesalers, restaurants and retail stores across the country and in Canada, Thomson said. They were also distributed in mesh sacks and cartons under the names TII Premium, El Competitor, Hartley, Onions 52, Imperial Fresh, Utah Onions and Food Lion.
Health officials recommend that consumers throw away any onions or foods made with onions supplied by Thomson, and in general throw away onions if they were unsure of where they came from.
The illness, named salmonellosis, can persist for four to seven days, the agency said. Children, older adults and people with weaker immune systems are most at risk to develop severe illness.
Symptoms include diarrhea, fever and abdominal cramps. Those who are severely ill may also experience