Why the German E. Coli Outbreak Was So Deadly

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University Hospital Meunster/Institute for Hygiene

The German E. coli outbreak has slipped from the news recently, as the rate of new cases and deaths has slowed. But it’s not over yet. On Thursday federal health officials announced that the death of a man in Arizona from a severe E. coli complication may be linked to the German outbreak. If so, he’d represent the first American to die in one of the worst food poisoning episodes in recent memory.

How bad has the German outbreak been? According to a new study [PDF] in the New England Journal of Medicine (NEJM), as of June 18 more than 3,200 people had fallen ill in that country thanks to E. coli, and 39 people had died. As far as we know, that’s the deadliest E. coli outbreak in history, outpacing on in Japan in 1996 that sickened nearly 10,000 people but killed only a handful.

The NEJM study — put together by members of the German team that helped investigate the current E. coli outbreak — is the most comprehensive look at the spread of the illness so far. Among its conclusions:

  • The outbreak began at the beginning of May and centered in northern Germany Cases peaked on May 22, when more than 200 people came down with the illness.
  • A quarter of the reported E. coli cases involved hemolytic-uremic syndrome (HUS), which can lead to acute kidney failure and eventually, death. Unusually for an E. coli outbreak, nearly all of the HUS patients were adults — children are usually the victims in similar outbreaks — and 68% were women, for reasons that still aren’t clear.
  • The causative agent was a non-O157 Shiga-toxin-producing E. coli strain, known as O104:H4. The strain isn’t exactly a new mutant, as some researchers originally thought, but a very rare strain that’s usually found in humans and not in animals.

But why was O104:H4 such a killer? In another study published Wednesday in the Lancet, researchers analyzed and sequenced the bacteria to determine what made it so usually deadly. As Hugh Pennington, a bacteriologist at the University of Aberdeen in Scotland, told HealthDay, the strain was able to release Shiga toxin — which can cause HUS—and had a propensity for sticking tightly to cells in the digestive tract:

It may well be so nasty because it combines the virulence factors of Shiga toxin, produced by E. coli O157, and the mechanism for sticking to intestinal cells used by another strain of E. coli, enteroaggregative E. coli, which is known to be an important cause of diarrhea in poorer countries.

E. coli hasn’t gone away. It still springs surprises.

It didn’t help that the strain was resistant to most — though not all — antibiotics. That antibiotic-resistance wasn’t necessarily a huge factor in the severity of the German outbreak, since antibiotics won’t do much to slow HUS once Shiga toxin has been released by the bacteria. But it’s a worrying sign that E. coli and other bugs are continuing to evolve in an arms race with our pharmaceuticals — and we may be losing.

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