The number of victims in the national outbreak of salmonella linked to raw chicken rose to 317 Friday, health officials reported.
The illnesses have been reported in 20 states and Puerto Rico, the Centers for Disease Control and Prevention said. The majority of cases, 73%, have been in California. No deaths have been reported.
The outbreak has been linked to chicken from three Foster Farms processing plants in central California, the Department of Agriculture said.
The company submitted a plan outlining "substantive changes to their slaughter and processing" to USDA on Thursday, said Dan Englejohn, with USDA's Food Safety Inspection Service. Based on that, the agency announced it would allow Foster Farms to continue operating the three plants.
In a statement, Foster Farms CEO Ron Foster said "we have worked relentlessly to address these issues and will continue to do so as we work to regain consumer trust and confidence in the Foster Farms brand."
The outbreak involves seven different strains of salmonella Heidelberg, said Christopher Braden, director of CDC's division of foodborne diseases. Several of the strains are resistant to at least one antibiotic and one is resistant to five, he said.
The outbreak has gained national attention in part because it is an especially virulent one. The CDC reports that 42% of those infected have been hospitalized, about double the usual rate for salmonella infections, said Braden.
The outbreak appears to be on-going. Two became ill after Sept. 24. It can take two to three weeks for a case to make its way through the public health system and be reported to CDC.