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How E coli spreads

No one need worry if they respect food hygiene.

What was initially dubbed "the Spanish cucumber disaster" is unravelling at an astonishing rate. Over a dozen Germans dead, thousands infected. E (short for Escherichia) coli is a common bacterium that dwells harmlessly inside our gut, and many labs propagate E coli as the standard life form in which to engineer genes. Some strains, however, can harm. The 0157 strain killed 20 people in the Scottish town of Wishaw in 1996-97.

The latest outbreak involves the 0104:H21 variant, which carries a gene encoding for a toxin that binds to human cells. Bursting gut cells cause diarrhoea, which turns bloody as local blood vessels are attacked. The toxin also binds to kidney cells, where it can cause fatal damage. Most cases of E coli are associated with contaminated meat, or direct contamination from farm animals. Patting a cow's excrement-flecked hide is enough to pick up the bug.

How might vegetables become affected though? Although cucumbers have now been ruled out, the current culprit still seems to be salad - and we know manure is in common use as a fertiliser, especially in organic farming.

Once a person is infected, an incubation period of one to 14 days ensues. Antibiotics can help, yet there's the risk of exacerbating kidney damage if they are taken too late. But the bacteria can easily be washed from vegetables and hands, so no one need worry if they respect food hygiene.

This piece appears in this week's New Statesman.

Tags:Science

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