Friday, October 22, 2010

Cholera: A Brief Look

Cholera is still a public health problem in many parts of the world because more than one billion people do not have access to safe water. In many poor countries, drinking water in rural areas as well as city slums is heavily contaminated with parasites, bacteria, and viruses. Public health experts estimate that about half of the world’s poor still suffer from waterborne diseases. Thousands died of cholera in India and Bangladesh in the 1960s and 1970s. Cholera outbreaks also occurred in Cambodia, Angola, Zimbabwe, Iraq, Sudan, Ethiopia, Somalia, Kenya, Uganda, and Peru. Sporadic cases of cholera in the United States were generally traced to consumption of seafood from the Gulf of Mexico. Travelers to areas where cholera is endemic have acquired the disease by drinking contaminated water or consuming contaminated food, particularly raw shellfish.

During serious cholera epidemics, mortality rates of about 50 to 60 percent are usually reported, but mortality rates as high as 80 percent have occurred during some outbreaks. Infectious disease experts believe that almost all cholera patients could be saved through the administration of intravenous liquids. Unfortunately, the medical resources needed for intravenous infusions are almost nonexistent in areas where cholera outbreaks and diarrheal diseases are common. Liquids given by mouth (oral hydration) are usually ineffective in cases of severe dehydration, but in the 1970s, researchers discovered that appropriate solutions of glucose and salts given by mouth were absorbed rapidly enough to save victims of cholera. Oral rehydration can also prevent most deaths from severe infantile diarrhea, even in the most primitive settings, if safe water is available. With proper oral or intravenous rehydration therapy, the case fatality rate is less than 1 percent.

The first twentieth-century cholera epidemic in South America was detected in Peru in 1991. About fourteen million people in Peru were infected, and 350,000 were hospitalized. Although the fatality rate was only about 1 percent, about thirty five hundred people died. Some cases were traced to contaminated food served in airplanes leaving Peru, proving again that an infectious disease anywhere in the world is just a plane ride away from any other point on the globe. The Pan American Health Organization reported that within six years of the 1991 outbreak in Peru, cholera had become established in fourteen countries because of inadequate water quality, sanitation, and hygiene. Thousands of cases and hundreds of deaths were reported, but experts suspect that only a fraction of all cholera cases are ever reported. Epidemiologists suggested that the cholera outbreaks were associated with unusually warm ocean currents that promoted the growth and spread of cholera vibrios carried by plankton, the mixture of microscopic plants and animals that drift in the ocean. Warmer waters promote their growth, thus increasing the chance of cholera epidemics wherever people lack access to safe water supplies and proper sanitary facilities. Misinformation about the 1991 cholera epidemic in Peru included claims that the disease appeared after chlorination of the water supply was discontinued. This was untrue because the water supply in the areas where the disease was most prevalent was quite primitive and was seldom, if ever, chlorinated or otherwise treated. Except in the capital city of Lima, Peru’s drinking water supplies at the time of the epidemic were generally not chlorinated.

At the beginning of the twenty-first century, cholera was still present in seventy-five countries and on all continents. Epidemiologists estimate that hundreds of thousands of people contract cholera every year, but the true extent of the threat is unknown because governments prefer to list deaths from cholera as gastroenteritis, intestinal flu, food poisoning, or other euphemisms for diarrheal diseases. A United Nations report published in 2006, Beyond Scarcity: Power, Poverty and the Global Water Crisis, estimated that more than one billion people get water for drinking, washing, and cooking from sources polluted by human and animal wastes. Diseases associated with the lack of safe water and adequate sanitation kill more than two million people in poor countries every year. Diarrhea and other diseases associated with dirty water and inadequate sanitation kill more than two million children every year. Cholera outbreaks continue to vindicate the sanitarian doctrine that poverty, pollution, and the lack of hygienic conditions are the most significant factors in generating and disseminating epidemic disease. Even prosperous, modern cities are vulnerable to the epidemic diseases that can emerge after natural disasters, such as floods, and man-made catastrophes, such as war and military occupation. When basic services—drinking water, sanitation, and health care—are disrupted, cholera and typhoid fever become significant public health risks, especially among refugees and displaced people.


Lois N. Magner
Praeger, 4/2009

Magner discusses the history behind major infectious diseases, how they are spread, and how to treat them.

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