E.coli Outbreak: How Epidemiology Saved the Day

Last week scientists solved the puzzle of the recent E.coli outbreak not by high-tech molecular techniques but by plain old interviewing.

The deadly bean sprouts were finally identified by a task force conducting interviews. They talked to all the people who had been infected and discovered that those who had eaten bean sprouts were nine times more likely to be ill than those who hadn’t. This was after lab tests of the bean sprouts had come back negative. There’s something amazing in human common sense making the link when the chemical work can’t.

The father of epidemiology was of course a perfect example of human logic. John Snow, the man who singlehandedly saved London from a cholera epidemic, was the inventor of the epidemiological method still used today. He was the first person to ever map a disease and he too found the source of an outbreak by simply talking to people.

On the 31st August 1854, cholera appeared in the houses of Soho. Within three days 127 people had died of it. Scientists at the time thought that it was being spread by ‘bad air’ or ‘miasmas’, but Snow disagreed. As a physician he had treated many patients with cholera and had not got sick from either breathing their air or from the patients themselves, something else had to be going on.

So, instead of running away from the epidemic like everyone else he walked straight into the middle of it. Snow began interviewing everyone around Broad Street, where the first cases had been. Talking to the residents he began making a map of who had got cholera and where. He began to notice that the cases were suspiciously clustered around the Broad Street water pump. It was beer however, that gave him one of the most important clues.

No-one in the local brewery was sick. The reason was of course that none of the workers had touched the water preferring to drink their beer instead. He presented this and other findings to the local council on the evening of the 7th of September. The situation by this point was critical, over 500 people had died in the time that Snow had been tracking the disease to its source.

The council were so convinced by him that they removed the water pump handle the next day and the outbreak began to stop. After the immediate threat had subsided however, Snow’s theory of water contamination by faeces was rejected and he had to fight his scientific corner on the subject for much of what remained of his life.

There is no question now that he was right. He died on the 16th June 1858 but the way Snow investigated the cause of that outbreak founded the methods of modern epidemiology that is tracking diseases to this day. His logical, practical and very human method is as valuable now as it was all those 157 years ago.

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