But the agency says there have been no reports of illness since December 12.
On Wednesday, the Public Health Agency of Canada announced it was no longer advising the public against eating romaine lettuce. Officials say that since the last illness started nearly a month ago, it's likely that any contaminated leafy greens that are linked to this outbreak are no longer on the market.
Still, the agency said it does not have enough information to recommend people in the USA avoid a particular food.
In a media statement, Halloran urged the CDC and Canadian officials to share their raw data on the outbreak and called on the FDA to request and review internal bacterial testing data from producers of romaine lettuce in order to pinpoint the source of the E. coli bacteria that has triggered the illnesses. She said it's still unclear whether FDA is intensifying testing of USA and imported products in the wake of Canada's findings. "Right now the CDC is saying it could be other leafy greens, but until we have more corroborating evidence, we continue to think it prudent to avoid romaine lettuce for now".
Pressure had been mounting on the CDC and the Food and Drug Administration (FDA) to provide more information to the public about this outbreak.
"People in these groups should be particularly vigilant about avoiding romaine lettuce", Rogers said. Illnesses started on dates from November 15 through December 12, 2017. Neither the CDC nor Canadian health officials have provided any information on where the romaine lettuce potentially involved in the illnesses was grown or processed, so for now, consumers should assume that any romaine lettuce, even when sold in bags and packages, could possibly be contaminated, Rogers said.
Last week, the CDC said it was eyeing leafy greens as the possible culprit and, this week, seem to be still looking for the source as the outbreak investigation continues.
The outbreak is responsible for 66 infections and two deaths in the two countries.
The symptoms of an E. coli O157:H7 infection include diarrhea that is bloody or watery, and severe stomach and abdominal cramps.
Outbreaks of toxin-producing E. coli are more typically linked to beef as the bacteria can get into the meat during slaughter and processing, especially ground beef, but infections from produce are not unheard of.
You can protect yourself by washing your hands thoroughly before and after preparing or eating food. Illnesses usually begin three to four days after eating food contaminated with this bacteria. People should also thoroughly wash fresh produce.