Epidemiology of cholera in the Americas

A persisting reservoir of the Gulf Coast strain of toxigenic V. cholerae O1 in Louisiana and Texas marshes and the shipment of seafood from these areas throughout the United States means that sporadic cases and outbreaks of cholera may occur anywhere in the country for the foreseeable future. Such cases are most likely to occur during warm months, especially between July and October. Physicians should think of cholera when consulted for severe watery diarrhea, even when the patient has no history of travel, and alert the laboratory. Experience has shown that US food and water sanitation is good enough to make either secondary transmission or large outbreaks unlikely; however, as long as we have foodborne and waterborne outbreaks of bacterial enteric diseases, the Gulf Coast strain may appear in a situation in which it can multiply and be ingested in large numbers by many people. The Latin American cholera epidemic has caused more cases of cholera in the United States in 2 years than the total of Gulf Coast strain cases identified during the past 20 years. The epidemic's future is uncertain. Despite knowing a great deal about cholera epidemiology, we cannot fully explain the ebb and flow of cholera epidemics. We do not know why cholera was apparently eliminated from the Western Hemisphere by 1900, nor can we predict which areas will be affected next or whether cholera will remain in a given area transiently or become endemic. The fact that cholera disappeared from the Western Hemisphere in the last century does not necessarily mean that it will disappear again. The situation is different now in several ways. The current pandemic is caused by the El Tor biotype, which persists better in the environment than does the classical biotype. Travel is now more frequent and more rapid. Finally, the population of the Western Hemisphere is about 14 times larger now than it was in 1850 and produces about 80,000 metric tons of human feces each day, of which only a fraction is treated. Thus, cholera will probably become endemic in Latin America and persist indefinitely.