Cholera is an acute epidemic infectious disease. It is characterized by watery diarrhoea, extreme loss of fluid and electrolytes, and severe dehydration. It can be fatal.
Cholera can be defined as an acute diarrhoeal infection caused by ingestion of food or water contaminated with the bacterium Vibrio cholerae. These bacteria were discovered in 1883. The German bacteriologist, Robert Koch (1843-1910), studied the disease during an epidemic in Egypt. He found a bacterium in the intestines of those who had died of cholera but could neither isolate the organism nor infect animals with it.
Later that year, Koch went to India, where he succeeded in isolating the bacteria. He discovered that they thrived in damp, dirty linen and moist earth, and in the stools of patients with the disease.
Cholera remains a global threat to public health and an indicator of inequity and lack of social development. Researchers have estimated that every year, there are roughly 1.3 to 4.0 million cases, and 21,000 to 14,000 deaths worldwide due to cholera. Cholera affects both children and adults and can kill within hours if untreated.
Cholera is most common in places with poor sanitation, crowding, war, and famine. Common locations include parts of Africa, south Asia, and Latin America.
Among people who develop symptoms, the majority have mild or moderate symptoms, while a minority develop acute watery diarrhoea. About one in 20 people infected have severe watery diarrhoea accompanied by vomiting, which can quickly lead to dehydration.
Although many infected people may have minimal or no symptoms, they can still contribute to spread of the infection.
If symptoms appear, they will do so between 12 hours and 5 days after exposure. They range from mild or asymptomatic to severe.
They typically include:
Large volumes of explosive watery diarrhea, sometimes called "rice water stools" because it can look like water that has been used to wash rice
A person with cholera can quickly lose fluids, up to 20 litres a day, which causes severe dehydration and shock can occur.
Signs of dehydration include:
Loss of skin elasticity (the ability to return to original position quickly if pinched)
Dry mucous membranes, including the inside of the mouth, throat, nose, and eyelids
Decreased secretion, for example, less sweating
Fast heart beat
Low blood pressure
Dizziness or light-headedness
Rapid weight loss
If not treated, dehydration can lead to shock and death in a matter of hours, especially among children and infants. Death can occur in otherwise healthy adults within hours. Those who recover usually have long-term immunity against re-infection.
Vibrio cholerae, the bacterium that causes cholera, is usually found in food or water contaminated by faeces from a person with the infection.
They can also enter by eating seafood that is raw or not completely cooked, in particular shellfish native to estuary environments, such as oysters or crabs.
Common sources include:
Municipal water supplies
Ice made from municipal water
Foods and drinks sold by street vendors
Vegetables grown with water containing human wastes
Raw or undercooked fish and seafood caught in waters polluted with sewage
When a person consumes the contaminated food or water, the bacteria release a toxin in the intestines that produces severe diarrhoea.
In situations where sanitation is severely challenged, such as in refugee camps or communities with highly limited water resources, a single affected victim can contaminate all the water for an entire population.
It is not likely you will catch cholera just from casual contact with an infected person.
Diagnosis and Treatment
A doctor may suspect cholera if a patient has severe watery diarrhoea, vomiting, and rapid dehydration, especially if they have recently travelled to a place that has a recent history of cholera, or poor sanitation, or if they have recently consumed shellfish.
A stool sample will be sent to a laboratory for testing, but if cholera is suspected, the patient must begin treatment even before the results come back.
It is normally dehydration that leads to death from cholera, so the most important treatment is to give oral hydration solution (ORS), also known as oral rehydration therapy (ORT).
The treatment consists of large volumes of water mixed with a blend of sugar and salts.
Pre-packaged mixtures are commercially available, but widespread distribution in developing countries is limited by cost, so homemade ORS recipes are often used, with common household ingredients.
Severe cases of cholera require intravenous fluid replacement. An adult weighing 70 kilograms will need at least 7 litres of intravenous fluids.
Antibiotics can shorten the duration of the illness, but the WHO does not recommend mass use of antibiotics for cholera, because of the growing risk of bacterial resistance.
Anti-diarrheal medicines are not used because they prevent the bacteria from being flushed out of the body.
Research has shown that zinc compliments may decrease and shorten the duration of diarrhoea in children with cholera.
With proper care and treatment, the fatality rate should be around 1 percent.
There are currently three cholera vaccines recommended by the World Health Organization (WHO). These are Dukoral, Shanchol, and Euvichol.
All three require two doses to give full protection.
Dukoral needs to be taken with clean water, and it provides roughly 65 percent protection for 2 years. Shanchol and Euvichol do not need to be taken with water, and they provide 65 percent protection for 5 years. All the vaccines offer higher protection nearer to the time they are given.
Everyone is susceptible to cholera, with the exception of infants who derive immunity from nursing mothers who have previously had cholera. Still, certain factors can make you more vulnerable to the disease or more likely to experience severe signs and symptoms. Risk factors for cholera include:
Poor sanitary conditions. Cholera is more likely to flourish in situations where a sanitary environment — including a safe water supply — is difficult to maintain. Such conditions are common to refugee camps, impoverished countries, and areas devastated by famine, war or natural disasters.
Reduced or nonexistent stomach acid (hypochlorhydria or achlorhydria). Cholera bacteria can't survive in an acidic environment, and ordinary stomach acid often serves as a first-line defense against infection. But people with low levels of stomach acid — such as children, older adults, and people who take antacids, H-2 blockers or proton pump inhibitors — lack this protection, so they're at greater risk of cholera.
Household exposure. You're at significantly increased risk of cholera if you live with someone who has the disease.
Type O blood. For reasons that aren't entirely clear, people with type O blood are twice as likely to develop cholera as are people with other blood types.
Raw or undercooked shellfish. Although large-scale cholera outbreaks no longer occur in industrialized nations, eating shellfish from waters known to harbor the bacteria greatly increases your risk.
Preventing Cholera and Reducing Risk
Be sure to use the bottled, boiled, or chemically disinfected water for the following purposes:
Preparing food or drinks
Brushing your teeth
Washing your face and hands
Washing dishes and utensils that you use to eat or prepare food
Washing fruits and vegetables
When travelling to areas where the disease is endemic, it is important to:
Eat only fruit you have peeled
Avoid salads, raw fish, and uncooked vegetables
Ensure that food is thoroughly cooked
Make sure water is bottled or boiled and safe to consume
Avoid street food, as this can carry cholera and other diseases
Wash hands with soap and water frequently, especially after using the toilet and before handling food. Rub soapy, wet hands together for at least 15 seconds before rinsing. If soap and water aren't available, use an alcohol-based hand sanitizer.
Be wary of dairy foods, including ice cream, which is often contaminated, and unpasteurized milk.
Cholera is an acute diarrhoeal disease that can kill within hours if left untreated.
Researchers have estimated that each year there are 1.3 to 4.0 million cases of cholera, and 21,000 to 143,000 deaths worldwide due to cholera.
Most of those infected will have no or mild symptoms, and can be successfully treated with oral rehydration solution.
Severe cases will need rapid treatment with intravenous fluids and antibiotics.
Provision of safe water and sanitation is critical to control the transmission of cholera and other waterborne diseases.
Oral cholera vaccines are an additional way to control cholera, but should not replace conventional control measures.
Safe oral cholera vaccines should be used in conjunction with improvements in water and sanitation to control cholera outbreaks and for prevention in areas known to be high risk for cholera.