(CNN) Federal health officials reported seven additional cases of E. coli illness Wednesday in a deadly E. coli outbreak that has now struck 15 US states.

The US Centers for Disease Control and Prevention said the total number of those infected has climbed to 24. Nine of those people have been hospitalized, two of whom are suffering from a form of kidney failure. There has been one death, which was previously reported

Maryland and New Jersey now join California, Connecticut, Illinois, Indiana, Michigan, Nebraska, New Hampshire, New York, Ohio, Pennsylvania, Vermont, Virginia and Washington, which all previously reported cases of illness.

All the sick individuals began feeling ill between November 15 and December 12.

This is about the same timing of an outbreak of E. coli in Canada, which health officials declared over on Wednesday

In all, 42 people, from five provinces, became ill, according to Public Health Agency Canada. One of those people died. Canadian health officials previously identified romaine lettuce as the cause of the outbreak there.

The cases in the United States are the same strain as the cases in Canada and some of them have the same genetic fingerprint.

Last week the CDC said it was eying leafy greens as the possible culprit and this week seem to be still looking for the source as the outbreak investigation continues.

"The likely source of the outbreak in the United States appears to be leafy greens, but officials have not specifically identified a type of leafy greens eaten by people who became ill," the CDC said Wednesday.

However, officials indicated the outbreak in the United States may also be over soon.

"Leafy greens typically have a short shelf life, and since the last illness started a month ago, it is likely that contaminated leafy greens linked to this outbreak are no longer available for sale," the CDC said.

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In Canada, health officials said romaine lettuce is now safe to eat. "The Public Health Agency of Canada is no longer advising individuals in affected provinces to consider consuming other types of lettuce, instead of romaine lettuce."

Symptoms of E. coli typically begin two to eight days after consuming the bacteria. They include severe stomach cramps, diarrhea and vomiting. Most people recover from the illness in five to seven days. Some individuals may develop a severe illness called hemolytic uremic syndrome, or HUS, which can be life-threatening, although most people recover in a few weeks. Those most at risk for E. coli illness include the very young, very old, and individuals with compromised immune systems.