(WJBK) - Four more deaths have been linked to a national food poisoning outbreak blamed on tainted lettuce, bringing the total to five.
Health officials have tied the E. coli outbreak, the largest in a decade, to romaine lettuce grown in Yuma, Arizona.
In an update Friday, health officials said 25 more cases have been added, raising the total number of illnesses to 197 in 35 states. At least 89 people were hospitalized.
Previously one death had been reported, in California. On Friday, health officials said they had learned of four more -- one in Arkansas, one in New York, and two in Minnesota.
The first illnesses occurred in March, and the most recent began on May 12, according to the Centers for Disease Control and Prevention.
The growing season in Yuma, Arizona ended six weeks ago, and it's unlikely any tainted lettuce is still in stores or people's homes, given its short shelf life. But there can be a lag in reporting, and reports of illnesses have continued to come in.
Many of the new cases were people who became ill two to three weeks ago, when contaminated lettuce was still being sold. Some said they did not eat romaine lettuce but were in close contact with someone who got sick after eating it.
Meanwhile, government authorities are still trying to figure out how and why the outbreak happened.
They haven't been able yet to trace the affected lettuce back to one particular farm, processor or distributor, FDA authorities said in an update Thursday.
"We are actively evaluating a number of theories about how romaine lettuce grown on multiple farms in the same growing region could have become contaminated around the same time," Dr. Scott Gottlieb and Dr. Stephen Ostroff wrote. Gottlieb is Commissioner of the U.S. Food and Drug Administration, and Ostroff is FDA’s Deputy Commissioner for Foods and Veterinary Medicine.
But since the growing season has ended, and affected lettuce is now off the shelves, the FDA may never get their answer.
Most E. coli bacteria are not harmful, but some produce toxins that can cause severe illness. People who get sick from toxin-producing E. coli come down with symptoms about three to four days after swallowing the germ, with many suffering bloody diarrhea, severe stomach cramps and vomiting.
Most people recover within a week, but some illnesses can last longer and be more severe.
The Associated Press contributed to this report