By David Beasley
ATLANTA (Reuters) - The number of suspected U.S. cases involving a deadly E.coli bacteria that has sickened thousands in Europe remained at four on Sunday, a Centers for Disease Control and Prevention spokeswoman said.
"Right now there have been no reports of any additional suspected cases" in the United States, CDC spokeswoman Lola Russell told Reuters.
All four U.S. patients recently visited Hamburg, Germany, officials said.
The rare strain of E.coli has infected people in 12 countries. It has killed 22 people and made more than 2,000 ill.
German-grown beansprouts and other sprouts could be the source of the deadly outbreak, German officials said.
There are no indications the U.S. food supply has been tainted by E.coli, U.S. Food and Drug Administration spokesman Siobhan DeLancey told Reuters on Sunday.
However, as a safety precaution, the FDA said it was conducting increased surveillance of fresh tomatoes, cucumbers, lettuce and raw salads imported from areas of concern. But officials said countries in the European Union are not a significant source of fresh produce for the United States.
The CDC said three suspected cases of a type of kidney failure associated with E.coli infections -- hemolytic uremic syndrome (HUS) -- had been identified in Massachusetts, Michigan and Wisconsin.
A fourth suspected case of diarrhea caused by the E.coli is under investigation, the CDC said.
Symptoms of E.coli infections include severe stomach cramps, diarrhea and vomiting.
Symptoms of the HUS kidney failure, which usually develop a week after diarrhea begins, include decreased frequency of urination, fatigue and losing pink color to skin and membranes due to anemia, the CDC said.
(Editing by Colleen Jenkins and Jerry Norton)