Hugh Pennington, professor of bacteriology, says E-coli outbreak is a "German problem"

German officials have set up a task force to hunt the source of a highly toxic strain of E-coli that has left at least 19 people dead in 12 countries across Europe.

Health authorities repeated warnings on Friday to avoid some raw vegetables in northern Germany, as officials said 199 new cases of the rare strain of the bacteria had been reported in the past two days.

But the warnings came as a European Union laboratory in Rome said there was no scientific evidence that vegetables were the source of the infection.

E-coli 0104 bacteria has claimed the lives of 19 people across Europe, the World Health Organisation [WHO] said on Friday, in a strain it said has "never [been] seen before".

Almost all but one of the bacteria-related deaths and further 1,700 infections identified occurred in Germany.

Seven people in Britain, who recently travelled to Germany, have been infected with the bacteria, Britain's health protection agency said.

Three of those infected were British nationals who had recently travelled to Germany and four were German nationals, the agency said.

Ban on food imports

Protests have surrounded the bacteria outbreak, particularly from Spanish fruit and vegetable growers who arrived in Hamburg on Friday to voice their innocence after Germany's admittance to wrongfully blaming the outbreak on Spanish cucumbers.

Germany, however, persisted with a ban on all imports on vegetables from European Union [EU] nations while Vladimir Putin, the Russian prime minister, asserted his country's decision to ban the produce. Putin said he would not allow his countrymen to be "poisoned" for the sake of joining the World Trade Organisation.

However, Hugh Pennington, professor of bacteriology at the University of Aberdeen in Scotland, told Al Jazeera that the outbreak is a "German problem".

"It remains a North German problem. The only people who have fallen ill are people who have been to Germany and have had food there," he said.

Pennington said that a case could be made for the banning of produce from EU countries, but that he did not think that "there is any case at all for banning food from any other country other than Germany because there is absolutely no evidence that any other produce from any other country has been involved in this outbreak".

"You could say, 'well, yes, let's be cautious about importing any German vegetables, but not from other countries, and particularly countries like Spain where there's absolutely no evidence that this bug lives at all."

Source of bug

The exact strain of E-coli is proving difficult to identify. Pennington said that because it is a "brand new bug", scientists are currently unable to determine where it is living.

"It hasn't been found in any food, despite food being looked at. The Germans think that the foods that are under suspicion [are] because people who have fallen ill have eaten lots of them.

He said that these foods include tomatoes, cucumbers and lettuce but that these are a part of a wide range of foods.

"But," he added, "no tests have found in any of this particular outbreak-strain on those foods".

E-coli is a common bacteria found in meat, vegetables and fruit. It normally lives in the intestines of people and animals where it helps the body break down food. There are hundreds of E-coli strains but some are harmful.

Problems emerge when the bacteria travels outside of the intestine. Most infections attack the bladder, kidney and blood stream.

To avoid foodborne illnesses, WHO recommends people wash their hands before eating or cooking food, separating raw and cooked meat from other foods, thoroughly cooking food, and washing fruits and vegetables, especially if eaten raw.

Source: Al Jazeera and agencies