Water-borne killers.

• Author: Platt, Anne
• Position: Infectious diseases from contaminated water

In the global resurgence of infectious diseases, the flow of water - for drinking, sanitation, and irrigation - is playing a central role.

Along the dying Aral Sea, in central Asia, the people are dying too - of cancer, typhoid, and hepatitis. The rivers that fed the sea are now largely diverted for irrigation; the water left for drinking bears toxins and diseases. Along the Danube River in eastern Europe, communities are losing millions of dollars because the water is too polluted to support a fishing industry - or to attract tourists. In these and many other places around the world, the health of people, their societies, and the land itself is being undermined by the sickness of the water. Healing our water is therefore an essential task - for preserving both human and ecological health.

For one out of every five people in the world, having enough clean water to drink and bathe in is a life-or-death issue. Eighty percent of all disease in developing countries is spread by consuming unsafe water. In those regions, waterborne pathogens and pollution kill 25 million people every year - a toll that amounts to one-third of all developing country deaths. The diseases that do most of the killing - diseases like malaria, cholera, and typhoid - are today primarily tropical: three-quarters of the victims they claim live in the tropics. But to some degree, every population on earth is threatened by waterborne diseases, and the pollution that so often accompanies them. Globally, about 250 million new cases of infection are reported every year - that's nearly the population of the United States.

This tragedy has its roots in two very basic and very common social problems: lack of clean drinking water, and lack of sanitation. Of course, these problems are closely related: in communities without adequate sanitation, pathogen-laden human and animal wastes, food, and garbage pile up near homes, or drain into waterways to infect drinking supplies. A whole range of diarrheal diseases is transmitted through this fecal-oral route: Hepatitis A, typhoid fever, cholera, salmonella - even roundworms. In 1993, the most recent year for which data were available, there were more than 1.8 billion cases of diarrhea worldwide, predominantly in Sub-Saharan Africa. Every year, diarrhea alone kills nearly 3 million children under age five, accounting for a full quarter of the deaths in this age group.

When one of these pathogens makes its way from sewage into a freestanding body of water, the stage is set for an epidemic. All it may take is a drink, a swim, or a meal of contaminated fish to become infected. An outbreak of cholera that began in Peru in 1991, for example, gradually contaminated the water supplies of every country in Latin America except for Paraguay and Uruguay, infecting more than 500,000 people before it subsided two years later. In Peru, the disease got around the ordinary preventive measures, such as boiling drinking water, because many people were consuming the bacterium by eating ceviche - raw fish with lemon juice. About 90 percent of cholera outbreaks are caused by inadequate sanitation.

Other diseases work variations on the same theme. Schistosomiasis, for instance, is a snail-borne illness caused by a parasite that penetrates human skin, and causes cirrhosis of the liver, intestinal and urinary tract damage, and anemia. The disease is endemic to certain parts of Africa, Asia, and South America, where it infects farmers and fishers who spend a lot of time wading through the shallow waters favored by the snails. About 200 million people are thought to be at risk. Onchocerciasis, or river blindness, affects some 18 million people in west Africa, especially in Cameroon and Nigeria. This parasite is carried by a blackfly that breeds along the region's slow-moving streams. It causes severe lesions around the eyes; about 10 percent of the cases result in blindness.

In addition to microbial diseases, our waters are spreading what could be called industrial diseases, as they absorb toxic chemicals from factories, nitrates from fertilizers, phosphates from household detergents - a growing list of synthetic chemicals of virtually every description. And other forms of environmental degradation are also taking a toll. Loss of forests and the resulting erosion clogs rivers with sediment; loss of wetlands disrupts nutrient cycles. These and similar stresses are greatly weakening the ability of natural waterways to absorb, filter, and process wastes naturally.

The "rivers of life" is a metaphor that must be as old as human consciousness. But now our rivers and lakes have also become reservoirs of sickness and death. In the United States, nearly 40 percent of rivers and streams are too dangerous for fishing and swimming, let alone drinking. In Russia, the Volga, the Dvina, and the Ob Rivers harbor strains of cholera, typhoid, dysentery, and viral hepatitis. (Russians depend on all of these rivers for drinking water.) In some parts of the world, rivers are so contaminated by industrial and human waste that no available treatment system could offer adequate protection. The same processes are at work in lakes, and even seas. (See "Dying Seas," January/February 1995.) The Black Sea, for instance, is choking to death from high levels of nutrient pollution. The pollution fosters algal blooms that are suffocating the fisheries, which form the basis of the region's local economy. All over the world, the health of aquatic ecosystems is deteriorating, and so is the health of their inhabitants, human and otherwise.

RUNNING JUST TO STAY IN PLACE

During a cholera outbreak in London in 1854, most people blamed their suffering on the rotting garbage in the streets or on some invisible evil in the air. But a local doctor named John Snow succeeded in tracing the infection to contaminated drinking water. That conceptual breakthrough opened the way for one of the most significant public health improvements the world had ever seen - the installation of comprehensive urban sewage systems in western Europe and the United States. By the late 19th century, improvements in water supply and sewage systems were having a dramatic effect on urban public health in these areas. In French cities, for example, such improvements correlate closely with an increase in life expectancy from about 32 years in 1850 to about 45 years by 1900.

Yet more than a century after Snow's discovery, we have not managed to find a way to break the grip of cholera and other waterborne diseases in much of the developing world. The most significant attempt occurred during the 1980s, which the U.N. declared the "International Drinking Water Supply and Sanitation Decade." The point of this program was to move from a state...