Four more people have died from tainted romaine lettuce, federal health officials said Friday, bringing the total to five deaths related to a virulent strain of E. coli whose source has still not been located.
In addition, officials at the Centers for Disease Control and Prevention updated the case count: 197 people from 35 states were sickened.
Food and Drug Administration officials said, however, that romaine now for sale on grocery shelves is safe to eat. The growing season in the Yuma, Ariz. region, which produced the contaminated lettuce, ended April 16. According to an FDA blog post, “Any contaminated product from the Yuma growing region has already worked its way through the food supply and is no longer available for consumption. So any immediate risk is gone.”
The F.D.A. said its investigators were still working to trace sources of the outbreak. This spring federal investigators traced the virulent strain of E. coli to the Yuma growing region. But they are still looking for the precise source — whether it originated in the water supply, harvesting equipment, a processing plant in the area or somewhere else.
The disclosure of more deaths followed a federal announcement two weeks ago that the danger had passed. Officials from the C.D.C. and the F.D.A. emphasized that almost all these illnesses were contracted during the window when the lettuce was still for sale. The last reported illness began on May 12. There is typically a lag between the time when someone falls ill and the C.D.C. is alerted.
Some of the ill patients had not eaten romaine themselves but became sick through contact with others who had, the C.D.C. said.
According to the agency, most people who become sick start experiencing symptoms three to four days after consuming produce tainted by Shiga-toxin producing E.coli O157:H7. Most recover within a week. Symptoms can include bloody diarrhea, vomiting, and severe stomach cramps.
Many patients in this outbreak became so ill that they needed to be hospitalized, including 26 who developed a type of kidney failure called hemolytic uremic syndrome.