Three people in the U.S. have been hospitalized because of the outbreak. While the Food and Drug Administration assured people the produce in the U.S. is safe, officials are stepping up food testing in Germany and Spain.
Meanwhile, the CDC continues to investigate the cause of the outbreak. German scientists believe lettuce, cucumbers and tomatoes may be the source. Signs pointed to Germany as the place it originated.
Twelve countries are now reporting cases, including the three people in the U.S. Experts call this virulent strain of E. coli a verotoxin.
"And this E. coli bacteria makes a toxin, it gets into your blood," said Dr. Frank Esper, who is an infectious disease expert. "And in some of the most serious cases it shuts down the kidneys."
Antibiotics are not indicated for treating this infection. Studies have suggested it may increase the chances of kidney failure.
German health authorities recommend people in Germany avoid eating raw tomatoes, fresh cucumbers, and leafy salads, until further notice.
"I have no reason to believe that what's specifically occurring in Europe is somehow going to happen over here," said U.S. Secretary of Agriculture Tom Vilsack.
Still, the CDC has put local hospitals on alert for any patients with signs of E. coli infection.
"Anybody who is experiencing any symptoms of diarrhea, particularly bloody," said R.N. Nancy Parris from St. Joseph's Medical Center. "If they have stomach cramps, low-grade fever. Those are the typical symptoms of this particular illness."
More than 1,700 people worldwide have been infected by the highly toxic E. coli. At least 18 people have been confirmed dead.
Besides avoiding certain foods, experts say good hygiene is another way to avoid food borne illness.
"People should use a separate chopping block for raw vegetables and for meat," said Perris. "Because you don't want to contaminate your salad or your raw vegetables that you'll be eating. Wash their hands before touching food. Wash their hands after using the toilet, and at appropriate opportunities."
European health officials say the number of cases peaked on May 22 and have been dropping ever since. But experts caution that the outbreak is not over yet.