The deadly food poisoning outbreak in Germany is being caused by a highly toxic strain of E.coli that has never been detected in an outbreak before, the World Health Organisation says.
German scientists are still searching for the source of the outbreak, which has killed 18 people and infected at least 1600. Seventeen of the deaths were in Germany, one in Sweden.
The gastrointestinal infection can cause a potentially fatal complication that affects the blood and kidneys.
World Health Organisation (WHO) said the strain says it appears to be a hybrid of two different bacteria.
Scientists at the Beijing Genomics Institute in Shenzhen, China, said the bug carried genes that made it resistant to several classes of antibiotics.
The head of the Robert Koch Institute, which monitors the infection in Germany, said the outbreak could last for months and that the source may never be known, the BBC reports.
Cases have been reported in at least 10 European countries and the United States, although almost all those outside Germany are in people who had recently been there.
The source of the infection, originally blamed on Spanish cucumbers, is unknown.
Russia has banned the import of raw vegetables from the European Union.