Ten other European nations and the U.S. have reported 90 other cases, all but two related to visits in northern Germany.

The Korean professors said the 29-year-old woman was hospitalized in August 2004 after suffering stomach pains and internal bleeding.

She was diagnosed with hemolytic-uremic syndrome (HUS), which is normally caused by enterohemorrhagic E. coli (EHEC) O157:H7. But doctors later found a different strain, E. coli O104:H4, in her stool sample.

She was released after four weeks of treatment.

"The patient had eaten a hamburger and first she was treated for diarrhea," Bae said. "Her symptoms got worse, and they were more serious than usual symptoms for typical E. coli infection."

They reported the case in the Yonse Medical Journal in 2006. It was the first paper that claim that the EHEC O104 strain could also cause HUS.

"No major research on E. coli followed that paper," Jang said. "And there's not been any outbreak before the recent one in Europe."

Jang said he would have to compare the Korean case with other E. coli cases.

“There are different kinds of O104:H4 and they seem to have particular genes that cause HUS," the professor said.

The elusive source of killer bug is still puzzling European authorities.

German media reported Saturday that 17 persons fell ill with E. coli after they ate in the northern German city of Luebeck last month, and that researchers from Germany's national disease control center were inspecting the restaurant.

Other media said health experts were investigating whether the disease first spread at a festival in the northern city of Hamburg last month that was visited by 1.5 million people.

Those sickened at the Luebeck restaurant included eight women who participated in a workshop in the city, a group of tourists from Denmark and a child from southern Germany.

``The restaurant is not responsible for this, however by looking at their delivery companies, we may be able to find out how and from where the bacteria spread,'' Werner Solback, a microbiologist from the university hospital in Luebeck, was quoted as telling the Luebecker Nachrichten paper.

The news magazine Focus reported Saturday that the first patients were hospitalized a week after the Hamburg festival and said the national disease control center, the Robert Koch Institute, assumes that many people likely were infected there. The institute has not discussed this theory and could not be reached for comment Saturday.

German Health Minister Daniel Bahr, meanwhile, warned Saturday that the cause of the infection may still be active.

“We have to continue to be alert,'' Bahr told daily paper Ruhr Nachrichten. ``Health officials are working nonstop to find the cause for all the infections, however, from outbreaks in the past we know that often the cause cannot be clearly identified.'' (From news reports)