Cholera in the 21st Century
By George Rutherford, MD
Cholera is an infectious disease caused by the free-living aquatic toxigenic bacterium, Vibrio cholerae serogroups O1 (biotypes Classical and El Tor) or O139 that presents with acute profuse diarrhea and can progress to severe dehydration and circulatory collapse. The infection is transmitted by consumption of contaminated water or more rarely by contaminated food. Case fatality can exceed 22% when treatment, which is aimed at rehydration, is delayed (1). Primary prevention consists of improvements in water and sewage systems to assure that cross-contamination does not occur. There are three safe, immunogenic and effective oral cholera vaccines worldwide; their use is mostly confined to travelers (2). Secondary prevention consists of replacing extracellular and intracellular fluid lost through diarrhea. One of the most remarkable public health advances in the second half of the 20th century was the introduction of oral rehydration salts (ORS), which are mixed with water for rehydration by mouth, rather than intravenously, and has markedly reduced deaths from cholera (3). Cholera has virtually been eliminated from the United States because of the ubiquity of advanced water and sewage treatment systems, and what residual disease that remains is among travelers returning from endemic areas. The most dramatic importation involved 75 passengers on an airline flight from Buenos Aires to Lima to Los Angeles where infection was associated with eating a cold seafood salad that had been brought aboard in Lima (4).
The seventh cholera pandemic began in 1961 and is most pronounced in sub-Saharan Africa and certain South and Southeast Asian countries. In 2005, the World Health Organization reported a total of 131,943 cases of cholera worldwide and 2,272 deaths (case fatality rate, 1.7%) in 52 countries; 97% of cases were reported from sub-Saharan Africa (5).
Shantytowns in low-income countries without municipal water or sewage systems are not dissimilar from London during the epidemic of 1854 immortalized by John Snow (6). As many as 1.1 billion people worldwide do not have access to piped water, and waterborne diseases overall may cause up to 2 million diarrheal deaths each year in children under 5. The United Nations Millennium Development Goal for Water is to reduce by half the proportion of persons without sustainable access to safe drinking water by 2015.
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