NORRIS: The bacterium behind all the trouble in Europe is similar to the dreaded E. Coli that has caused occasional deadly outbreaks in the U.S. and elsewhere. But as we just heard, scientists know far less about the strain that's hit Germany.

As NPR's Richard Harris reports, researchers are puzzling over exactly why it's causing so many deaths, and how long the epidemic will last.

RICHARD HARRIS: The bacterium that struck Germany may be obscure, but medical scientists know quite a bit about its method of attack.

Dr. ROBERT TAUXE (U.S. Centers For Disease Control and Prevention): To cause disease, it really has to do two things. It has to attach to the intestinal wall and then produce toxin that gets absorbed into the body.

HARRIS: Dr. Robert Tauxe at the U.S. Centers For Disease Control and Prevention says the bacteria actually produces the same toxins that come from the more familiar E. Coli O157:H7. But the germ in Europe uses a different method to attach to the intestine. And it's caused so many deaths, that's left medical researchers wondering whether the bacterium's method of attack is especially deadly or if it simply has spread to a whole lot of people.

Dr. TAUXE: Well, that's the key question, and the answer is not entirely clear.

HARRIS: This is somewhat uncharted territory. A Chinese genetic lab reported today that they actually sequenced the DNA of the germ, and they consider it a new variant. But Dr. Tauxe says the strain of E. Coli is actually not entirely new.

Dr. TAUXE: We have not seen outbreaks in contaminated food before, but there have been isolated cases identified in the past, in a number of different countries around the world.

HARRIS: Dr. Phillip Tarr from Washington University in St. Louis has seen more than his share of disease caused by this sort of bacteria. He is a pediatrician who has treated children afflicted with other dangerous strains of E. Coli.

Dr. PHILLIP TARR (Washington University): What we think happens is the toxins get into the bloodstream and injure the blood vessels. And the blood vessels form little clots and there's impaired blood flow to organs throughout the body.

HARRIS: This condition is called hemolytic uremic syndrome, and it hits the kidneys hard. In Germany, 470 people have been diagnosed with this severe condition. Usually, Tarr says, more than half of people who get this disease need kidney dialysis.

Dr. TARR: In almost all cases it's temporary. Dialysis lasts a median of about eight days.

HARRIS: But dialysis doesn't save everybody, as is clearly the case in Europe. Tarr says obviously the first priority now is to figure out the best care for people currently sickened by the disease.

Dr. TARR: But after this is over, we really need to determine how it could have been prevented, if possible, and how to prevent it looking forward. And right now we need to know where it's coming from.

HARRIS: Surveys of people who got sick found they were more likely to have eaten fresh tomatoes, lettuce and cucumbers. But that doesn't prove that the disease is actually from vegetables. And even if they can prove that link, Dr. Tauxe from the CDC says that begs the question of where the vegetables came from.

Dr. TAUXE: Tracing back the origin of fresh produce, we learned in this country, can take a long time. And I'm sure it's the same in Germany.

HARRIS: And that case could also be getting cold. People diagnosed today could have eaten bad food a week or two ago. And with that lag time, the epidemic will probably fizzle out slowly, Tauxe says. Also, if the contaminated food is a fresh vegetable, the normal food safety tips won't necessarily protect you.

Dr. TAUXE: Unfortunately, these bacteria tend to be sticky and it's difficult to wash them off and sometimes they're even inside.

HARRIS: So this is one time when boiled cabbage could actually start to sound like an appealing option.

Richard Harris, NPR News.

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