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- Patient Comments: Cholera - Symptoms and Signs
- Patient Comments: Cholera - Treatments
- Cholera facts
- What is cholera?
- What is the history of cholera?
- What are cholera symptoms and signs?
- What causes cholera, and how is cholera transmitted?
- What are risk factors for cholera, and where do cholera outbreaks occur?
- Is cholera contagious?
- What is the incubation period for cholera?
- What is the contagious period for cholera?
- What physicians usually treat cholera?
- How do health-care professionals diagnose cholera?
- What is the treatment for cholera?
- Is it possible to prevent cholera? Are cholera vaccines available?
- What is the prognosis of cholera?
- Where can people find more information about cholera?
Quick GuideTravel Health: Vaccines & Preventing Diseases Abroad
What causes cholera, and how is cholera transmitted?
Cholera is caused by the bacterium V. cholerae. This bacterium is Gram stain-negative, comma-shaped, and has a flagellum (a long, tapering, projecting part) for motility and pili (hairlike structures) used to attach to tissue. Although there are many V. cholerae serotypes that can produce cholera symptoms, the O groups O1 and O139, which also produce a toxin, cause the most severe symptoms of cholera. O groups consist of different lipopolysaccharides-protein structures on the surface of bacteria that are distinguished by immunological techniques.
The toxin produced by these V. cholerae serotypes is an enterotoxin composed of two subunits, A and B; the genetic information for the synthesis of these subunits is encoded on plasmids (genetic elements separate from the bacterial chromosome). In addition, another plasmid type encodes for a pilus (a hollow hairlike structure that supports bacterial attachment to human cells and facilitate the movement of toxin from V. cholerae into human cells). The enterotoxin causes human cells to extract water and electrolytes from the body (mainly the upper gastrointestinal tract) and pump it into the intestinal lumen where the fluid and electrolytes are excreted as diarrheal fluid. The enterotoxin is similar to toxin formed by bacteria that cause diphtheria in that both bacterial types secret the toxins into their surrounding environment where the toxin then enters the human cells. The bacteria are usually transmitted by drinking contaminated water, but the bacteria can also be ingested in contaminated food, especially seafood such as raw oysters.
What are risk factors for cholera, and where do cholera outbreaks occur?
Everyone who drinks or eats food that has not been treated to eliminate V. cholerae (liquids need to be chemically treated, boiled, or pasteurized, and foods need to be cleaned and cooked), especially in areas of the world where cholera is present, is at risk for cholera.
Outbreaks occur when there are disasters or other reasons for a loss of sanitary human waste disposal and the lack of safe fluids and foods for people to ingest. Haiti, a country that had not seen a cholera outbreak in over 50 years, had such circumstances develop in 2010 after a massive earthquake destroyed sanitary facilities and water and food treatment facilities for many Haitians. V. cholerae bacteria eventually contaminated primary water sources, resulting in over 530,000 people diagnosed with cholera that resulted in over 7,000 deaths. This cholera outbreak spread to Haiti's neighbor, the Dominican Republic. The Vibrio cholerae strain was closely related to a strain found in Nepal and leads some individuals to blame Nepalese troops that helped with the earthquake disaster as the source of the Haiti cholera outbreak.
In third-world countries, hunger can lead people to inadvertently eat contaminated food and/or drink contaminated water, thus raising the risk for cholera to infect malnourished populations.
There is some evidence that V. cholerae can survive in saltwater and have been isolated from shellfish; eating raw oysters is considered a risk factor for cholera, especially in underdeveloped countries and occasionally even in developed countries. A few people are diagnosed with cholera every year in the U.S. Most of the individuals diagnosed are travelers who were exposed to cholera outside the country, but occasionally, isolated cases are traced to contaminated seafood, usually from states that border the Gulf of Mexico.
Some individuals are at higher risk to become infected than others. People who are malnourished or immune-compromised are more likely to get the disease. Children ages 2-4 seem more susceptible than older children, according to some investigators. In addition, researchers have noted that patients with blood type O are twice as likely to develop cholera as others. The reason for this blood type susceptibility is not completely understood. People with achlorhydria (reduced acid secretion in the stomach) and people taking medicines to reduce stomach acid (H2 blockers and others) are also more likely to develop cholera because stomach acid kills many types of bacteria, including V. cholerae.