"Most of the newly reported cases are people who became sick two to three weeks ago, still within the window when contaminated romaine was available for sale", said the CDC statement. On Friday, health officials said they have learned of four more - another in California as well as one each in Arkansas, Minnesota and NY.
Overall, five deaths have been reported in Arkansas, California, Minnesota and NY.
The US Food and Drug Administration (FDA), which is investigating the outbreak alongside the CDC, believes that the probable link to all these illnesses is romaine lettuce sourced from the winter growing areas in and around the Yuma region in Arizona.
As of May 30 the investigation figures show 197 people infected with the outbreak strain of E. coli O157:H7 have been reported from 35 states. Of 187 people with information available, 89 (48 percent) have been hospitalized, including 26 people who developed hemolytic uremic syndrome, a type of kidney failure.
Almost half of those who became ill had to be hospitalized.
Most E. coli bacteria are not harmful, but some produce toxins that can cause severe illness. While almost 90 percent of those who fell ill reported eating romaine lettuce in the week before they were sickened, some told the CDC that they did not personally eat the lettuce but were in close contact with somebody who did.
Romaine lettuce grows near Soledad, California, U.S., May 3, 2017. People who get sick from toxin-producing E. coli come down with symptoms about three to four days after consumption, with many suffering bloody diarrhea, severe stomach cramps and vomiting.
While most people recover within a week, some illnesses can last longer and be more severe, the CDC cautioned.