Gert Lindemann, the agriculture minister in the northern state of Lower Saxony, said in Hanover that Germans should not eat sprouts until further notice, with definitive test results available Monday. Mr. Lindemann said that the authorities could not yet rule out other possible sources for the outbreak and urged Germans to continue avoiding tomatoes, cucumbers and lettuce.
The suggestion that sprouts may be the cause of the outbreak, one of the most catastrophic food-borne illnesses in years, was met with caution by public health experts.
“We would want either epidemiological evidence or confirmed laboratory evidence,” said Dr. Robert Tauxe, deputy director of food-borne diseases for the Centers for Disease Control and Prevention in Atlanta.
The German authorities had acted prematurely once before in their investigation, blaming cucumbers grown in Spain for the outbreak after preliminary tests showed that they might have contained toxic E. coli bacteria. Further tests showed that the Spanish cucumbers did not contain the strain making people sick, and investigators then backtracked.
That episode infuriated Spanish farmers who lost tens of millions of dollars in sales and were forced to abandon ripe vegetables to rot in the fields, as demand collapsed.
The outbreak in Germany, which the health authorities first reported in late May, is caused by a rare strain of toxic E. coli that can cause bloody diarrhea. In extreme cases it can cause acute kidney failure and death. In previous outbreaks involving other strains of E. coli, kidney failure appeared most often among children. In this outbreak, most victims with kidney failure have been adults and more than two-thirds have been women.
The outbreak showed no signs of abating on Sunday, with Germany’s national disease control center reporting that the death toll had risen to 22 and that 2,153 people were ill, more than 600 of them in intensive care.
Mr. Lindemann said that locally grown bean sprouts were the “most convincing” cause, and that the farm that grew them in the Uelzen area had been shut down. But he said 18 sprout mixtures were under suspicion, including sprouts of beans, broccoli, peas, chickpeas, garlic, lentils, mung beans and radishes. The sprouts are often used in mixed salads.
The suspect farm’s produce — including herbs, fruits, flowers and potatoes — was impounded. At least one of the farm’s employees was also infected with the E. coli bacteria, Mr. Lindemann said.
Some experts in food-borne illnesses expressed surprise at Mr. Lindemann’s announcement, not because sprouts were an unlikely source of the deadly bacteria but for the opposite reason: sprouts have long been associated with food-borne illness and are a food most commonly suspected in this sort of outbreak. As such, the experts said, sprouts should have been among the first foods scrutinized by investigators.
Dr. Tauxe, who has talked to European officials during the investigation, though not on Sunday, said sprouts were included in a questionnaire that German investigators had used to interview victims of the outbreak to determine what they had eaten. He said that the officials in charge of the investigation had been aware of the common link between sprouts and food-borne illness.
“It’s not something they’re likely to have missed,” Dr. Tauxe said.
American experts said that investigators of any such outbreak in the United States would have been sure to have examined the possibility that sprouts might have been the cause.
“This is one of the things that everybody in our local health departments knows, that if you hear about one person eating sprouts you’re supposed to ring the alarm bell,” said William E. Keene, a senior epidemiologist of the Oregon Public Health Division, who has investigated many outbreaks involving sprouts. “A single case in a salmonella or E. coli O157 outbreak is a red flag,” he said, referring to the most common E. coli bacteria.
Since 1996, sprouts have been linked to at least 30 illness outbreaks, according to a United States federal food safety Web site that warns that children, the elderly, pregnant women and people with weak immune systems should not eat uncooked sprouts.
Sprouts were found to be the cause of one of the most severe series of outbreaks of E. coli ever identified, in Japan in 1996. In those outbreaks about 10,000 people, many of them children, fell ill after eating food containing uncooked radish sprouts. That involved the common O157:H7 strain of E. coli. The current outbreak in Germany involves a rare strain known as O104:H4.
Bacteria can flourish in the warm, humid conditions in which sprouts are grown, according to a report by the Centers for Disease Control. Investigators have sometimes found that the seeds used to grow sprouts are contaminated with bad bacteria, like E. coli or salmonella. Once those seeds start growing, the bacteria can easily spread.
“If you’re concerned about your risk of food-borne illness, don’t eat sprouts,” Dr. Keene said. “They’re essentially a dangerous kind of food.”
The Spanish government did not comment Sunday on the latest news in the German investigation. But mounting evidence that the problem should never have been linked to produce from Spanish farms is likely to raise pressure on Germany and the European Union to compensate Spanish farmers for estimated weekly losses of $286 million in revenue because of canceled shipments, as well as massive job cuts among seasonal growers in Andalusia.
That area, the Spanish agricultural heartland, was already suffering the worst unemployment problem in the country.
Judy Dempsey reported from Berlin, and William Neuman from New York. Raphael Minder contributed reporting from Madrid.
