One person died. Health officials said the tainted lettuce was grown in Yuma, Arizona.
The CDC regularly publishes any new updates in the outbreak and has advised against buying or eating any romaine lettuce that you can not confirm came from outside the Yuma region.
"Based on the ongoing USA outbreak investigation, and the information provided by individuals who became sick, the likely source of the outbreak in Canada is romaine lettuce", said PHAC, in a statement.
Genetic testing shows that the E. coli strain involved in the outbreak produces a specific type of "Shiga toxin" that causes more severe illness, Wise explained.
The most recent illness started on April 25, said the CDC, noting that illnesses since then may not have been reported yet to the agency. The bacteria recently killed one person in California, marking the first fatality tied to the outbreak. No recalls have been issued in direct connection to the Escherichia coli O157:H7 outbreak.
Sixty-four people have been hospitalized, the CDC said and 17 of those have developed hemolytic uremic syndrome, a form of kidney failure that can be life-threatening, although most people recover in a few weeks.
Officials say other area farms could also be affected since numerous E. coli poisoning cases can be traced to chopped lettuce sold in bagged form to restaurants that didn't come from that Yuma farm.
One farm was found by the Food and Drug Administration to be the source of the whole-head romaine lettuce that sickened several people at a correctional facility in Alaska.
"State and local health officials continue to interview ill people to ask about the foods they ate and other exposures they had before they became ill", the CDC writes in its latest report. "If you do not know if the lettuce in a salad mix is romaine, do not eat it".
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Ahead of his trip Mr Johnson said: 'On so numerous world's foreign policy challenges the United Kingdom and U.S. are in lockstep. That may change on Tuesday, with an expected announcement by Trump on future USA support for the deal.