Kolera

Cholera, caused by the bacteria Vibrio cholerae, is rare in the United States and other industrialized nations. However, globally, cholera cases have increased steadily since 2005 and the disease still occurs in many places including Africa, Southeast Asia, and Haiti. CDC responds to cholera outbreaks across the world using its Global Water, Sanitation and Hygiene (WASH) expertise.

Cholera can be life-threatening but it is easily prevented and treated. Travelers, public health and medical professionals and outbreak responders should be aware of areas with high rates of cholera, know how the disease spreads, and what to do to prevent it.

Cholera is an acute, diarrheal illness caused by infection of the intestine with the bacterium Vibrio cholerae and is transmitted by contaminated food or water. The infection is often mild or without symptoms, but sometimes it can be severe.

Approximately 5–10% of persons will have severe cholera which in the early stages includes:

• profuse watery diarrhea, sometimes described as “rice-water stools,”
• vomiting
• rapid heart rate
• loss of skin elasticity
• dry mucous membranes
• low blood pressure
• thirst
• muscle cramps
• restlessness or irritability

Persons with severe cholera can develop acute renal failure, severe electrolyte imbalances and coma. If untreated, severe dehydration can rapidly lead to shock and death.

Profuse diarrhea produced by cholera patients contains large amounts of infectious Vibrio cholerae bacteria that can infect others if ingested, and when these bacteria contaminate water or food will lead to additional cases. Dispose of human waste appropriately to prevent the spread of cholera.

Persons caring for cholera patients can avoid acquiring illness by washing their hands after touching anything that might be contaminated and properly disposing of contaminated items and human waste.

Infected persons, when treated rapidly, can recover quickly, and there are typically no long term consequences. Persons with cholera do not become carriers of the disease after they recover, but can be reinfected if exposed again.

Cholera is an acute intestinal infection causing profuse watery diarrhea, vomiting, circulatory collapse and shock. Many infections are milder diarrhea or are asymptomatic. If left untreated, 25-50% of typical cholera cases are fatal.

A person can get cholera by drinking water or eating food contaminated with the cholera bacterium. Large epidemics are often related to fecal contamination of water supplies or street vended foods. The disease is occasionally transmitted through eating raw or undercooked shellfish that are naturally contaminated.

Brackish and marine waters are a natural environment for the etiologic agents of cholera, Vibrio cholerae O1 or O139. There are no known animal hosts for Vibrio cholerae, however, the bacteria attach themselves easily to the chitin-containing shells of crabs, shrimps, and other shellfish, which can be a source for human infections when eaten raw or undercooked.

Cholera disease is caused by toxigenic Vibrio cholerae O-group 1 or O-group 139.

• Only toxigenic strains of serogroups O1 and O139 have caused widespread epidemics and are reportable to the World Health Organization (WHO) as "cholera".
• V. cholerae O1 has two biotypes, Classical and El Tor, and each biotype has two distinct serotypes, Inaba and Ogawa. The symptoms of infection are indistinguishable, although a higher proportion of persons infected with the El Tor biotype remains asymptomatic or have only a mild illness.
• In recent years, infections with the Classical biotype of Vibrio cholerae O1 have become quite rare and are limited to parts of Bangladesh and India.

Many other serogroups of Vibrio cholerae, with or without the cholera toxin gene, can cause a cholera-like illness, as can non-toxigenic strains of the O1 and O139 serogroups.

Click here for more information on illness caused by non-O1 and non-O139 V. cholerae serogroup infections.

Cholera is a major cause of epidemic diarrhea throughout the developing world. There has been an ongoing global pandemic in Asia, Africa and Latin America for the last four decades. In 2011, a total of 58 countries reported a cumulative total of 589,854 cases including 7,816 deaths (case fatality rate of 1.3%) to the World Health Organization (WHO). There was an 85% increase in number of cholera cases as a result of the Haiti cholera outbreak in October 2010. Resource-poor areas continue to report the vast majority of cases with the African continent having the worst case fatality rates ¹.

Large population migrations into urban centers in developing countries are straining existing water and sanitation infrastructure and increasing disease risk. Epidemics are a marker for poverty and lack of basic sanitation. Multiple routes of disease transmission mean that successful prevention may require different measures in different areas.

Natural infection and currently available vaccines offer incomplete protection of relatively short duration; no multivalent vaccines are available for O139 infections.

Simple rehydration treatment saves lives, but logistics of delivery in remote areas remains difficult during epidemic periods. Accompanying antibiotic treatment is helpful but may be difficult because of growing antimicrobial resistance. Natural reservoirs in warm coastal waters make eradication very unlikely.

It is almost impossible to distinguish a single patient with cholera from a patient infected by another pathogen that causes acute watery diarrhea without testing a stool sample. A review of clinical features of multiple patients who are part of a suspected outbreak of acute watery diarrhea can be helpful an identifying cholera because of the rapid spread of the disease.

While management of patients with acute watery diarrhea is similar regardless of the illness, it is important to identify cholera because of the potential for a wide spread outbreak.

Isolation and identification of Vibrio cholerae serogroup O1 or O139 by culture of a stool specimen remains the gold standard for the laboratory diagnosis of cholera.

Cary Blair media is ideal for transport, and the selective thiosulfate–citrate–bile salts agar (TCBS) is ideal for isolation and identification. Reagents for serogrouping Vibrio cholerae isolates are available in all state health department laboratories in the U.S. Commercially available rapid test kits are useful in epidemic settings but do not yield an isolate for antimicrobial susceptibility testing and subtyping, and should not be used for routine diagnosis.

In areas with limited to no laboratory testing, the Crystal VC® dipstick rapid test can provide an early warning to public health officials that an outbreak of cholera is occurring. However, the sensitivity and specificity of this test is not optimal. Therefore, it is recommended that fecal specimens that test positive for V. cholerae O1 and/or O139 by the Crystal VC® dipstick be confirmed using traditional culture-based methods suitable for the isolation and identification of V. cholerae.

Treatment: most persons infected with the cholera bacterium have mild diarrhea or no symptoms at all. Only a small proportion, about 10%, of persons infected with Vibrio cholerae O1 have illness requiring treatment at a health center.

Cholera patients should be evaluated and treated quickly. With proper treatment, even severely ill patients can be saved. Prompt restoration of lost fluids and salts through rehydration therapy is the primary goal of treatment.

Antibiotic treatment, which reduces fluid requirements and duration of illness, is indicated for severe cases of cholera.

Zinc treatment has also been shown to help improve cholera symptoms in children.