The Ghost Map: The Story of London’s Most Terrifying Epidemic — and How It Changed Science, Cities, and the Modern World by Steven Johnson. Riverhead Books, $26.95. 295 pages.
The News & Observer
October 29, 2006
English scientist solves deadly mystery
By PHILLIP MANNING
By the middle of the 19th century, London was the largest city in the world with two and half million people. It was also the foulest, with a woefully inadequate sewage system and 200,000 cesspools, many overflowing. The filth from both sources ended up in the Thames, which reeked of human excrement. One heat wave produced a stench so bad that newspapers dubbed it “The Big Stink,” and said “whoso once inhales the stink can never forget it.”
In addition to nose-boggling smells, London’s exuberant growth produced something else new. Cholera, unknown in the city until the 19th century, became a recurring and horrifyingly deadly visitor. One outbreak killed 14,000 Londoners. It was no great leap for residents to put the two together. Bad air caused cholera. To eliminate the disease, almost everyone agreed the city must clean up its air.
In his absorbing and beautifully crafted book, “The Ghost Map,” Steven Johnson tells how so many people could be so wrong for so long. And how it cost thousands of lives. The government approach, then as now, was to throw money and manpower at the problem. But the true mechanism of cholera transmission was established not by any of the governmental panels and committees set up to solve the problem. In a story line that hardly seems plausible today with our emphasis on huge multiperson science projects, one man working almost entirely alone finally defeated London’s cholera. His name was Dr. John Snow, a medical man, a loner with a knack for statistics and map making.
Cholera is caused by the bacterium Vibrio cholerae. If several million of them get into your gut, they will reproduce at a prodigious rate. You will quickly develop watery diarrhea and begin vomiting uncontrollably. Your body is reacting to the cholera’s toxin by expelling water, waste and millions of deadly bacteria. Unless you are one of the lucky ones, you will soon be dead. Think of it. You wake up healthy in the morning and die of cholera before the sun goes down. No wonder the government desperately wanted to clean up London’s cholera-causing air.
John Snow was one of the few Londoners not sold on the noxious-air theory. The men who worked on the city’s sewage lines (known as flushermen) and those who emptied cesspools breathed far more bad air than the ordinary citizen, yet Snow knew they were robust and healthy. Furthermore, if cholera came from nasty things in the air, why didn’t it attack the lungs rather than the gut? After much study, Snow hypothesized that cholera came from water — not air.
At the time, Londoners got their water from either neighborhood pumps or one of the water-supply companies that serviced the city. Snow found that districts using companies that drew water from the tidal reaches of the Thames where sewage was present had far higher death rates from cholera than those drinking water taken farther upstream. Snow was now convinced that bad water was the culprit, but he knew he would need more evidence to persuade bad-air partisans. He found it in 1854 when cholera again hit London.
The first victim was a little girl living at 40 Broad Street. To keep her clean after bouts of diarrhea, her mother regularly rinsed her diapers in a bucket and tossed the foul water into a cesspool. “That is how it began,” declares Johnson.
Up and down Broad Street, men, women and children contracted cholera. Some survived, most did not. Slogging doggedly through the ravaged neighborhood, Snow located the homes of the dead. Their houses clustered around a local water source — the Broad Street pump.
Snow presented his findings at an emergency meeting of the local Board of Governors. The board was skeptical. But lacking any other ideas, they agreed to remove the Broad Street pump’s handle.
The epidemic began to subside immediately. In another week it was over — along with the lives of 700 people. An engineering survey found that the walls of the cesspool at 40 Broad Street leaked directly into the well, confirming that those drinking from the Broad Street pump were inadvertently consuming bits of waste containing millions of invisible, but deadly, bacteria from the diapers of the unfortunate first victim of the epidemic.
Although Snow had stopped the cholera epidemic, government officials stuck stubbornly to the bad-air theory. “We do not find it established that water was contaminated,” one committee reported. To convince doubters, Snow prepared a map of the area, showing every pump and every house. He added a short black line for every person who died in the house. The ghost map showed a cluster of black lines around the Broad Street pump. It demonstrated clearly and graphically what Snow had been saying over and over again: cholera came from contaminated water. Few listened. Stopping cholera, government officials still believed, depended on cleaning the air by draining cesspools. So, for the wrong reasons, London began a gargantuan project to build a modern sewage system.
Five years later, as the project neared completion, London was on its way to becoming the healthiest city in the world. Then cholera struck again. Most of the deaths occurred in districts served by a water company that took its water from a tidal river ripe with sewage back flow. The link between the deaths and contaminated water was finally clear to everyone. Bad water, not bad air, was the source of cholera.
When London’s sewage lines were completed, the outlets were placed far downstream of the water companies’ inlet lines. Cholera has not visited the city since. And John Snow’s contribution to London’s public health was finally recognized. An 1866 editorial in Britain’s premier medical journal started with “The researches of Dr. Snow are among the most fruitful in modern medicine.” Unfortunately, Dr. Snow was not around to enjoy the accolades. He had died eight years earlier.
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