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.
The CDC said that some of the affected people had not eaten lettuce, but had contact with others who had fallen ill.
In the update Friday on the nation's largest E. coli outbreak in a decade, health officials said 25 new cases have been added, and at least 89 people were hospitalized.
Overall, five deaths have been reported in Arkansas, California, Minnesota and NY.
Officials say the people who became ill ate the tainted romaine lettuce from the Yuma, Arizona growing region when it was likely still available in grocery stores and restaurants. The last harvest was collected on April 16, and because the lettuce only has a 21-day shelf life, it is highly unlikely that any lettuce covered by the advisory is still available.
Officials said that first illness began sometime between March 13 and May 12.
"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.
The CDC has not pinpointed the exact source of the outbreak, but the lettuce appears to have been contaminated with Shiga toxin-producing E. coli O157:H7, a particularly unsafe strain of the bacteria.
Symptoms include diarrhea, which can be bloody, severe stomach cramps and vomiting. Of those three cases, two developed a potentially fatal condition called hemolytic uremic syndrome that sometimes leads to kidney failure.
The disclosure of more deaths followed a federal announcement two weeks ago that the danger had passed.