BERLIN — Across northern Germany, vegetables lie in untouched heaps in stores and markets. Hospitals are becoming overwhelmed, and medical investigators continue to hunt for the source of the deadly epidemic caused by an aggressive strain of E. coli bacteria, the worst outbreak in recent history.
An agriculture official in Hanover announced late Sunday that initial tests confirmed that bean sprouts grown in northern Germany are the likely cause of the outbreak that has killed at least 22 people and sickened more than 2,000.
Different kinds of sprouts from one organic farm in the greater Uelzen area, between the cities of Hamburg and Hanover, could be traced to infections in five German states, Lower Saxony Agriculture Minister Gert Lindemann told reporters.
"There were more and more indications in the last few hours that put the focus on this farm," he said at a news conference.
The outbreak began in northern Germany in mid-May with the first casualty reported on May 21. It has since spread to 12 countries.
At least 2,000 people have fallen ill with E. coli poisoning in Germany, and 627 of them have developed a life-threatening complication that can cause kidney failure.
Almost 100 additional cases of this type of E. coli poisoning have been reported in 11 other European countries and in the United States, where four people are infected. The only fatality outside Germany thus far was in Sweden. In that case and most others, the victims had recently visited northern Germany.
It is the third outbreak and the deadliest one involving E. coli in recent years, authorities said. A 1996 Japanese outbreak killed 12, and one in Canada in 2000 killed seven.
The epicenter of the outbreak has been the port city of Hamburg, which has reported more than 600 E. coli infections.
"Hospitals in the city are reaching the limits of their capacity," said city government spokesman Christoph Holstein, adding that they may not be able to cope if the situation gets much worse.
Hamburgs Eppendorf University Clinic alone has admitted more than 100 E. coli patients in the past three weeks, and treatment is constantly being adapted.
"The doctors are learning almost by the hour," said Christine Jaehn, a spokeswoman for the hospital.
She explained that, although 13 patients have been released, many of those who survive the infection may never completely recover full kidney function.
Across the northern part of the country, grocery stores threw out spoiling vegetables, and market vendors said they were losing thousands of dollars from the outbreak.
At cafes and restaurants in the region, waiters and managers said people were shunning salads and raw vegetables. Others put up signs announcing "safe" produce. Some just created alternatives.
At Caminito's Argentine deli in Berlin, the owner started offering rice instead of salad with his entrees and fretted over it.
"We eat pasta, not rice, in Argentina," he said, asking whether the rice tasted OK. "The customers don't want salad now."
Scientists are moving swiftly to learn more about the toxin-producing E. coli. Dag Harmsen, a microbiologist at the Muenster University Hospital, which has been closely involved in the investigation, said the researchers are hoping to know enough about the strain within a week to be able to prevent more infections and better treat patients.
"We are pretty sure we can soon tell in much more detail why this strain is so aggressive and spreads so widely," he said.
He explained that the toxic bug on the rampage in Germany is thought to be a hybrid of two strains.
Still, investigators have been on a trail of false leads in trying to find out how exactly the bacteria got into the food chain. The Robert Koch Institute was coerced to deny media reports that it suspected the source of the outbreak might have been a May 6-8 harbor festival in Hamburg that attracted 1.5 million visitors.
Now the institute's investigators are looking closely at supplies delivered to the Kartoffelkeller restaurant in the northern German city of Lubeck. Seventeen diners fell ill after eating a meal of steak and salad there on May 13.
One of them, a 48-year-old woman, has died of HUS. The owner of the restaurant, Joachim Berger, told public broadcaster ZDF that his produce came from a wholesaler in the central food market in Hamburg.
Authorities thought they had traced the source to organic Spanish cucumbers sold there, but subsequent tests showed that the vegetables were not contaminated with the same strain of bacteria causing the illnesses.
That discovery was made too late for many Spanish farmers. With thousands of tons of produce left unsold, it is estimated that the mistake in Hamburg has cost Spanish growers an estimated $290 million a week.
The food scare has led to a series of trade restrictions on European produce. Russia and Qatar are among the countries that have banned the import of vegetables from the European Union.
Russian Prime Minister Vladimir Putin dismissed criticism from the EU that Moscows move is disproportionate.
"People really are dying because of eating these products," he said. "We cannot let our people get poisoned."
People across Europe were playing it safe.
"I ask where the vegetables come from when I make my procurements now," said Jessica Eng, a vegetable vendor at the Saluhall market in Stockholm. "And I would not buy anything from Germany right now."
• This article is based in part on wire service reports.