Cholera is a serious, acute, infectious disease characterized by watery diarrhea that is caused by the bacterium Vibrio cholerae.
The bacterium Vibrio cholerae was first identified by Robert Koch in 1883 during a cholera outbreak in Egypt. The name of the disease comes from a Greek word meaning “flow of bile.” Cholera typically occurs in major outbreaks or epidemics, often after natural disasters such as hurricanes or tsunamis during which water supplies are contaminated.
Cholera is spread by eating food or drinking water that has been contaminated with V. cholerae. Contamination usually occurs when human feces from a person who has the disease contaminates a community water supply. Fruits and vegetables can be contaminated in areas where crops are fertilized with human feces. Cholera bacteria live in warm, brackish water and can infect persons who eat raw or undercooked seafood obtained from such waters. Cholera is rarely transmitted directly from one person to another. The disease is both preventable and treatable. Deaths usually occur in developing countries due to lack of access to hospitals and treatment.
The extensive system of sewage and water treatment in the United States, Canada, Europe, Japan, and Australia has virtually eliminated concern for visitors and residents of these countries. People visiting or living in other parts of the world, particularly the Indian subcontinent and in parts of Africa, Haiti, and South America, should be aware of the potential for contracting cholera and practice prevention.
Some people are at greater risk of having a severe case of cholera if they become infected. These risk factors include:
Although cholera was a public health problem in the United States and Europe a hundred years ago, modern sanitation and the treatment of drinking water have virtually eliminated the disease in developed countries. Only a few cases occur in the United States each year, most of which are acquired abroad. In 2015, the European Centre for Disease Prevention and Control (ECDC) reported only 24 cases of cholera in the European Union, of which 15 were in the United Kingdom. Subsequently, numbers were likely to rise as infected economic and war refugees migrate into Europe from less developed countries.
Anyone can get cholera, but infants, children, pregnant women, and elderly individuals are more likely to die from the disease because they become dehydrated faster. There is no season in which cholera is more likely to occur. In February 2018, major cholera outbreaks were reported in Yemen, the Democratic Republic of Congo, Tanzania, Zambia, Mozambique, Zimbabwe, Malawi, and Angola. People traveling to less developed countries can find current information on cholera and other contagious disease outbreaks on the CDC Travelers' Health web page.
Cholera is caused by the bacterium V. cholerae. This bacterium is a gram-negative aerobic bacillus, or rod-shaped bacterium. It has two major biotypes: classic and 01, also called El Tor. El Tor is the biotype responsible for most of the cholera outbreaks reported from 1961 through the 2000s.
V. cholerae is sensitive to acid, so most cholera-causing bacteria die in the acidic environment of the stomach. However, when a person has ingested food or water containing large amounts of cholera bacteria, some survive to infect the intestines. Antacid usage or the use of any medication that blocks or reduces acid production in the stomach allows more bacteria to survive and cause infection.
In the small intestine, the rapidly multiplying bacteria produce a toxin that causes a large volume of water and electrolytes to be secreted into the bowels and then to be abruptly eliminated in the form of watery diarrhea. Vomiting may also occur. Symptoms appear between one and three days after contaminated food or water has been ingested.
Signs of dehydration include intense thirst, little or no urine output, dry skin and mouth, an absence of tears, glassy or sunken eyes, muscle cramps, weakness, and rapid heart rate. The fontanelle (soft spot on an infant's head) will appear sunken or drawn in. Dehydration occurs most rapidly in the very young and the very old because these individuals have fewer fluid reserves. A doctor should be consulted immediately any time signs of severe dehydration occur. Immediate replacement of lost fluids and electrolytes is necessary to prevent kidney failure, coma, and death.
Rapid diagnosis of cholera can be made by examining a fresh stool sample under the microscope for the presence of V. cholerae bacteria. Cholera can also be diagnosed by culturing a stool sample in the laboratory to isolate the cholera-causing bacteria. In addition, a blood test may reveal the presence of antibodies against the cholera bacteria. In areas where cholera occurs often, patients are usually treated for diarrhea and vomiting symptoms as if they had cholera without laboratory confirmation because the onset of life-threatening dehydration is rapid.
Preventing dehydration by replacing fluids and electrolytes lost through diarrhea and vomiting is key for treating cholera. The discovery that rehydration can be accomplished orally revolutionized the treatment of cholera and similar diseases by making this simple, cost-effective treatment widely available throughout the world. WHO has developed an inexpensive oral rehydration solution (ORS) containing appropriate amounts of water, sugar, and salts that is used worldwide. In cases of severe dehydration, replacement fluids must be given intravenously. Patients are encouraged to drink when they can keep liquids down and eat when their appetite returns. Recovery generally takes three to six days.
Adults may be given the antibiotic tetracycline to shorten the duration of the illness and reduce fluid loss. WHO recommends this antibiotic treatment only in cases of severe dehydration. If antibiotics are overused, cholera bacteria may develop resistance to the drug, making the antibiotic ineffective in treating even severe cases of cholera. Tetracycline and doxycycline are not given to children whose permanent teeth have not come in because it can cause the teeth to become permanently discolored.
Other antibiotics used to speed up the clearance of V. cholerae from the body are azithromycin (Zithromax), doxycycline (Bio-Tab, Doryx, Vibramycin), ciprofloxacin (Cipro), and erythromycin.
The Centers for Disease Control and Prevention (CDC) has reported that the administration of zinc along with rehydration therapy and antibiotic therapy significantly shortens the duration and severity of diarrhea in children with cholera and several other diarrhea-causing diseases. The CDC recommends the use of zinc as a complementary treatment generally in children with significant diarrhea.
In developing countries, the public health challenge is much greater. Preventive measures following natural disasters include guaranteeing the purity of community drinking water, either by large-scale chlorination and boiling or by bringing in bottled or purified water from the outside. Other important preventive measures at the community level include provision for the safe disposal of human feces and good food hygiene. However, these measures are difficult to implement after natural disasters in less developed and less accessible parts of the world. Organizations such as WHO devote large amounts of money and staff to cholera prevention and treatment, especially providing supplies of ORS, during cholera outbreaks. In 2017, WHO launched an initiative to reduce cholera worldwide by 90%.
Cholera is a highly treatable disease so long as resources are available for rehydration. Patients with mild cases of cholera usually recover on their own in three to six days without additional complications. They may eliminate the bacteria in their feces for up to two weeks. Chronic carriers of the disease are rare. With prompt fluid and electrolyte replacement, the death rate in patients with severe cholera is less than 1%. Untreated, the death rate can be greater than 50%. The difficulty in treating severe cholera lies in getting medical care to the sick in developing areas of the world where medical resources are limited.
The best form of cholera prevention is to establish good sanitation and waste treatment systems. In the absence of adequate sewage treatment, the following guidelines should be followed to reduce the possibility of infection:
Cholera is one of the few infectious diseases that can be spread by human remains (through fecal matter leaking from corpses into the water supply). During natural disasters, emergency workers who handle human remains are at increased risk of infection. It is considered preferable to bury corpses rather than to cremate them, however, and to allow survivors time to conduct appropriate burial ceremonies or rituals. The remains should be disinfected prior to burial and buried at least 90 ft. (30 m) away from sources of drinking water.
Several cholera vaccines exist, but all have limitations. An older vaccine, Dukoral, is licensed in 60 countries but not in the United States and is prequalified by WHO. It is given orally in two doses and provides incomplete (roughly 25%–50%) immunity for 4–6 months. The other vaccine, Shanchol and Euvichol are also prequalification by WHO. They provide the advantages of longer protection and lower cost. In June 2016, the U.S. Food and Drug Administration approved Vaxchora, a single dose vaccine. As of 2018, the CDC does not recommend routine cholera vaccination for travelers. Residents of cholera-plagued areas should discuss the value of the vaccine with their doctor.
See also Communicable diseases ; Disease outbreaks ; Global Public Health ; Pandemic ; Vaccination .
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European Centre for Disease Prevention and Control, Gustav III:s Blvd. 40, Solna, 171 65, Sweden, +46 (0)8 586 010 00, Fax: +46 (0)8 586 010 01, email@example.com, https://ecdc.europa.eu/en/home .
United States Centers for Disease Control and Prevention (CDC), 1600 Clifton Rd., Atlanta, GA, 30329-4027, (404) 639-3534, (800) 232-4636, http://www.cdc.gov .
Tish Davidson, AM