Tuesday, March 18, 2008

Cholera: Tracking the First Truly Global Disease

Cities lacked the infrastructure needed to contend with the ever growing masses. As the population swelled, so did the pestilential odors that rose from the over 200,000 cesspools across the city and from the sewage that piled up in every ditch and alleyway. The sewage overflowed into houses and marketplaces from storm-water sewers during the frequent rainstorms and at the River Thames's high tide, said Jon Schladweiler, a historian with the Arizona Water and Pollution Control Association.

Much of this waste eventually made its way into streams or directly into the Thames. In England rivers were viewed as a waste-disposal system, and the Thames became a reeking brown sewer. This scenario was pervasive across Europe. "Disease, stench, and filth were rampant in cities throughout Europe at the time," Schladweiler said.

There was a lot of confusion about the disease, as in the early days of HIV, said Ralph Frerichs, professor of epidemiology at University of California, Los Angeles. Most physicians believed the disease was contracted by breathing noxious vapors, or miasma. "There was a lot of fear, because people can't stop breathing air," Frerichs said.

But one doctor, John Snow, published another theory in 1849: Cholera was transmitted by contaminated food or water. He argued that it couldn't be airborne because it didn't affect the lungs. But his theory was ignored, attacked by many among the medical profession because he couldn't identify the "poison" in the water.

It wasn't until the 1854 outbreak that Snow was able to prove his argument. He mapped the location of cholera deaths—and found high concentrations in certain areas. For example, about 500 people died in ten days near the intersection of Cambridge and Broad Streets—they shared a single water supply.

He went to city officials with his data. "He was very concerned about transmitting this information to the public and the Board of Guardians," Frerichs said. The board, a city-council-like body, was in charge of public health, welfare, and sanitation. The pump handle from the water source was removed—and cases in the area dropped to almost none.

At that time two companies supplied the city with water from the Thames, one located upstream, the other, downstream. Snow discovered that cholera was rampant among patrons whose water originated downstream—contaminated by city sewage.

The Water Act of 1852 required that water companies filter water. In 1866 Charles Greaves, the engineer from the East London Company, admitted that water from open reservoirs and the river had been pumped directly to the city without purification—though company officials later denied it. That year 4,500 people died in East London in the country's fourth cholera epidemic.

The Great Stink

By the summer of 1858, the metropolis was wrapped in "The Great Stink." The stench from the Thames had grown so intense that thousands of residents fled the city.

Windows of the Parliament building had to be covered with curtains soaked in chloride of lime to keep the government open—but Parliament ultimately closed down because the smell became unendurable. "This was one of the few times in history it's closed," Schladweiler said.

The repeated outbreaks of disease and unbearable odors prompted city officials to build new drains, protect the water supply, construct public bathhouses—and construct proper sewers.

The sewer-building project, designed by engineer Joseph Bazalgette, linked 1,000 miles (1,600 kilometers) of street sewers to 82 miles (132 kilometers) of huge, egg-shaped sewers that fed effluent out into the open sea. This new shape kept sewage flowing, even in flat landscapes like the Thames River Valley.

With better sanitation, the cholera epidemics stopped. In 1876 the comma-shaped bacterium was discovered under a microscope by the German doctor Robert Koch. Cholera was then fully recognized as an acute bacterial infection of the intestine caused by the intake of food or water contaminated with Vibrio cholerae, usually from human feces.

Bazalgette's novel design was adopted by city planners across Europe and in the U.S. Though it had to be prompted by epidemic disease and crowded, pestilential slums, England became the leader in the sciences of urban planning and public health.

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