Nonetheless, the major produce companies headquartered in the Salinas Valley have largely shifted their production to the Yuma region, which began shipping romaine a couple of weeks ago, Horsfall said.
The contaminated lettuce is likely still on the market, Gottlieb told The Associated Press in a phone interview.
"We did feel some pressure to draw conclusions as quickly as we could", he said.
Individuals who are sick say they ate romaine lettuce before their illnesses occurred, the Public Health Agency of Canada reports.
Most romaine sold this time of year is grown in California, Gottlieb said.
Although the outbreak is centred in Quebec and Ontario, grocery giants like, Loblaw, Sobeys and Walmart have made a decision to stop selling romaine lettuce at their stores nationwide.More news: Trump says doesn't want to hear 'suffering' Khashoggi tape
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States affected by the outbreak include California (which had the highest number of cases - 10), Michigan, Connecticut, Illinois, Massachusetts, Maryland, New Hampshire, New Jersey, New York, Ohio and Wisconsin. Mike Stuart from the Florida Fruit and Vegetable Association said sourcing the outbreak could take a while.
People living in those provinces should avoid eating romaine lettuce for now, the agency said.
The CDC said that the strain of the current outbreak has the "same DNA fingerprint as the E. coli strain isolated from ill people in a 2017 outbreak".
Njoo says the most recent illness began November 1 but a delay in reporting means the agency didn't find out about it until this week. But, as Anna Werner reports, tracking down the source of the contaminated produce is quite hard. That can mean the entire industry becomes implicated in outbreaks, even if not all products are contaminated.
"They have chose to wait until they find the source of the problem with the shipment that was making people sick, so we're really at the mercy now of when they do their research and when it comes back online again", said restaurant owner Brian Doherty.
Escherichia coli O157, sometimes called VTEC, is a bacterial infection that can cause severe stomach pain, bloody diarrhea and kidney failure.
First, it was the massive recall of Turkey.