BERLIN — Health officials now say four people in the U.S. may be linked to the food poisoning outbreak in Europe.
All four were in northern Germany in May and officials are confident that they were infected with E. coli in that country. Three of them — two women and a man — are hospitalized with a kidney complication that has become a hallmark of the outbreak.
Officials said Friday they are also checking two possible E. coli cases in U.S. military service members in Germany.
The source of the outbreak hasn't been pinpointed but salad vegetables are suspected.
An official from the Food and Drug Administration says produce in the U.S. remains safe. The government has stepped up testing of imported food from Germany and Spain, but very little is imported from those countries.
The number of people sickened by a mysterious strain of E. coli in Europe is still rising more than a month after it was first detected, but officials say there are now signs the bacterial outbreak responsible for at least 18 deaths could be slowing.
Since the first case of a patient in Germany detected with the bacteria on May 1, the country's national disease control center reported Friday that there are now 1,733 people in the country who have been sickened, including 520 suffering from a life-threatening complication that can cause kidney failure.
The World Health Organization said that 10 other European nations and the U.S. have reported a total of 90 people sick from the bacteria, all but two of whom had recently visited northern Germany or, in one case, had contact with a visitor from the region.
Though nearly 200 new cases of E. coli infection were reported in Germany in the first two days of June, the Robert Koch Institute disease control center said new infections peaked on May 21 and May 22, and have since then been dropping.
Though it cautioned that what appears to be a downward trend could change if there are new cases that have not yet been reported, there are other signs that the outbreak could be waning.
Kidney specialist Dr. Reinhard Brunkhorst, the president of the German Nephrology Society, told reporters in Hamburg that hospitals are now seeing fewer new infections reported each day, though cautioned that "it may be less, but it's not over yet."
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"There is no reason for hysteria, because it's not spreading and it's not increasing — it's decreasing," he said.
While suspicion has fallen on raw tomatoes, cucumbers and lettuce as the source of the germ, researchers have been unable to pinpoint the food responsible. Racing to curb the spread of the killer food bug, the German government set up a national task force Friday to hunt down the source of the highly toxic bacterial strain.
The outbreak is considered the third-largest involving E. coli in recent world history, and it is already the deadliest. Twelve people died in a 1996 Japanese outbreak that reportedly sickened more than 9,000, and seven died in a Canadian outbreak in 2000.
Researcher Dag Harmsen at the Muenster University Hospital, which has been closely involved in the investigation of the outbreak, said that scientists were hoping to know enough about the E. coli strain by next week to be able to prevent new infections and better treat patients.
The WHO recommends that to avoid food-borne illnesses, people wash their hands, keep raw meat separate from other foods, thoroughly cook their food, and wash fruits and vegetables, especially if eaten raw. Experts also recommend peeling raw fruits and vegetables if possible.
Nearly 200 new cases of E. coli infection were reported in Germany in the first two days of June, the national disease control center reported Friday, but officials say there are signs the European outbreak could be slowing.
The Robert Koch Institute said that there are now 1,733 people in Germany — the epicenter of the outbreak — who have been sickened, including 520 suffering from a life-threatening complication that can cause kidney failure.
On Friday, the WHO cautioned people against taking antibiotics if they fall ill. The U.N. health agency said it supports existing recommendations to avoid antibiotics, because self-medication can increase the chance that the bacteria will develop further drug resistance.
Anti-diarrhea medication also should be avoided because it stops the bacteria from quickly leaving the body, WHO epidemiologist Andrea Ellis told reporters in Geneva.
Some German doctors have recommended that certain patients should be treated with antibiotics.
"If there are particular cases in which that's what the bedside physician has deemed appropriate, then there would probably be good reasons for that," Ellis said.
"But in general we don't want people to pull some antibiotics that they might have sitting around at home," she said. "In addition, anti-diarrheals are generally not recommended."
The four sickened American travelers, who had recently been to Germany, fell ill due to the toxic bacteria, but they are unlikely to spark a spreading outbreak in the U.S., say food safety experts who urge both common sense and caution.Story: U.S. risks from E. coli outbreak remain low, experts say
“These humans aren’t going to introduce this strain into the U.S. and have it become a permanent, common resident,” said Dr. Timothy Jones, an epidemiologist who serves on the federal Food and Drug Administration’s Food Safety committee.
Strain has rarely seen 'glue'
Scientists probing the deadly E. coli strain in Europe are finding the bacteria combines a highly poisonous, but common, toxin with a rarely seen "glue" that binds it to a patient's intestines.
It may take months for the global team of researchers to fully understand the characteristics of the bacteria. But they fear this E. coli strain is the most toxic yet to hit a human population.
Most Escherichia coli or E. coli bacteria are harmless. The strain that is sickening people in Germany and other parts of Europe, known as 0104:H4, is part of a class of bacteria known as Shiga toxin-producing Escherichia coli, or STEC.
This class has the ability to stick to intestinal walls where it pumps out toxins, causing diarrhea and vomiting. In severe cases, it causes hemolytic uremic syndrome or HUS, attacking the kidneys and causing coma, seizure and stroke.
Market collapse in Spain
As the number of consumers avoiding vegetables grows, European farmers say they are losing millions of euros every day.
Russia on Thursday extended a ban on vegetables from Spain and Germany to the entire European Union to try to stop the outbreak spreading east, a move the EU quickly called disproportionate and Italy's farmers denounced as "absurd." No deaths or infections have been reported in Russia.
Russian Prime Minister Vladimir Putin on Friday rejected the EU claim, saying that authorities in Russia can't risk population's health by allowing EU vegetable imports at a time when the authorities in countries affected have failed to determine the cause of the outbreak.
Meanwhile, Chancellor Angela Merkel agreed with Spanish Prime Minister Jose Luis Rodriguez Zapatero in a telephone conversation late Thursday to push for EU help for affected farmers, Merkel's spokesman said.
Merkel, however, also defended the decision of state officials in Hamburg to announce their suspicions that Spanish cucumbers were the possible source of the outbreak. The warning was given after three cucumbers from Spain tested positive for E. coli, but further tests then revealed that it was a different strain to the one that has sickened so many people in the northern port city and elsewhere.
"The chancellor indicated great understanding for the urgent economic situation in the Spanish produce sector," spokesman Steffen Seibert said.
"At the same time she noted the responsibility of the German agencies to keep citizens informed in all phases and to report test results to the European early warning system."
In the southern Spanish tourist resort town of Torremolinos, Spaniards handed out about 7 tons of cucumbers free to the public in a show of support for the farmers affected by the outbreak who have seen their market collapse
The Associated Press, Reuters and msnbc.com's JoNel Aleccia contributed to this report