Cholera Is Still With Us: 5 Things to Know

David A. Sack, MD

Disclosures

October 25, 2018

1. Cholera can kill by causing severe dehydration.

Cholera, a bacterial infection of the small intestine, is characterized by acute watery diarrhea and can lead to severe, life-threatening dehydration within a few hours. The causative agent for cholera is Vibrio cholerae, serotype O1, which is spread through contaminated water or food. Annually, about 2.8 million people become infected and approximately 95,000 die of the disease.[1]

Cholera originated from the Ganges Delta of Bangladesh and India, where it remains endemic and continues year-round, with variable seasonal patterns of risk. Strains from the Ganges Delta have spread to Africa, other parts of Asia, and Latin America (including Haiti).[2] When cholera strains were introduced to these other geographic areas, they caused severe, and often prolonged, outbreaks. In some areas of Africa, including the Democratic Republic of Congo, Nigeria, and Mozambique, cholera is now endemic and cases are reported year after year. In other areas, outbreaks appear to be self-limited and seem to disappear for a few years before returning again. Although the pattern is different between countries, many countries have specific "hotspot" regions where cholera tends to occur most often.[3,4]

The bacteria—V cholerae—colonize the small intestine where they secrete a potent enterotoxin. This toxin does not damage the intestinal lining but leads to the overproduction of cyclic AMP, which results in a tremendous outpouring of salts and water from the intestinal mucosa. So much fluid is secreted that it overwhelms the gut's ability to reabsorb, resulting in watery diarrhea and vomiting. Because patients with cholera lose so much sodium, bicarbonate, and potassium—along with the water in the diarrhea fluid—they quickly become dehydrated and experience metabolic acidosis and potassium deficiency, which can lead to death if not treated.

2. Although it's a medical emergency, cholera is easily treated.

Cholera can quickly kill a patient, but it can also be easily treated with appropriate fluids and antibiotics. Without treatment, the case fatality rate of patients with severe cholera is about 50%, and most deaths occur within the first day. An individual, of any age or sex, can be perfectly healthy in the morning and be dead in the afternoon. Cholera is thus a medical emergency, and patients must get to a proper medical facility quickly where rehydration fluids can be administered. With rapid and effective rehydration, no one should die if they get to a health facility and still have a breath, even if they arrive without a detectable pulse.

It's estimated that a severely dehydrated patient in shock has lost about 10% of their body weight because they have lost so much fluid. A volume of fluid equal to 10% of the patient's body weight must be replaced quickly. For such patients, Ringer's lactate intravenous solution should be given rapidly to restore fluid and electrolyte balance. With less severe dehydration, oral rehydration solution (ORS)—a solution of salts and water with a carbohydrate, either glucose or rice starch—can be used to rehydrate patients. Continued intake of ORS is needed to replace ongoing fluid loss after the initial rehydration. After vomiting has stopped, an oral antibiotic—usually single-dose doxycycline—should be given to reduce the purging and shorten the illness. The antibiotic also keeps the bacteria from spreading to others in the family and neighborhood when the patient returns home. For outbreaks in which the strain is resistant to doxycycline, azithromycin is used.

3. Cholera is a disease of inequity.

Previously, cholera used to affect all socioeconomic strata, but as water and sanitation conditions improved for most people, the poor were often left behind. Middle-class and wealthy individuals who live in countries at risk for cholera have increasing access to safe water and improved toilets, but the poor still lack these resources. So, when cholera outbreaks occur, they afflict the poorest and most vulnerable. Not only is this population most at risk for disease, but they are also the most likely to die because they lack access to rapidly available medical care. When medical care is needed quickly, the poorest suffer the most.

4. Climate change threatens to increase cholera outbreaks.

Cholera transmission is linked to unsafe water and poor sanitation, but transmission is also related to environmental factors, including climate change. V cholerae is not transmitted in areas with safe water and good sanitation. Therefore, if cholera-prone countries were able to improve the conditions of water and sanitation, cholera would cease as it has in industrialized countries. Thus, the long-term solution for controlling cholera will depend on improving the availability of safe water and sanitation.

Environmental and climate factors also determine the risk and rates of cholera. Many regions in developing countries have very poor water and sanitation infrastructure, yet cholera is rare or has not been seen. Other areas experience cholera on a seasonal basis, yet the water and sanitation situation continues to be poor throughout the year. The seasonal factors that determine cholera risk are a key area of research and will be very important to understand, especially in view of concerns regarding climate change and the potential that cholera will increase as the earth warms.

Cholera risk and climate change are related in several ways, but two stand out.[5] First, Vibrio infections increase during the warmer months; therefore, as the oceans and planet warm, one would expect cholera seasons to be prolonged. The second threat relates to the rising sea levels in delta areas like Bangladesh. As the land disappears, people will be forced out of their homes to live in much more densely populated areas, where cholera can spread easily.

5. We now have a vaccine against cholera.

Use of an inexpensive oral vaccine, when integrated with improved water and sanitation, promises to significantly reduce the threat of cholera globally.[6] Since the 1960s, we have known how to treat patients and save their lives, but we have not made sufficient progress on reducing transmission. Theoretically, if we had been able to increase access to safe water and improved sanitation for all, cholera risk would be decreasing, but these improvements have lagged.

Recently, a new oral cholera vaccine has become available.[7] The vaccine is safe, inexpensive (less than $1.50 per dose), and effective, and provides new optimism for cholera control. By providing vaccine to people living in "hotspot" areas and targeting improvements in water and sanitation in high-risk locations, the Global Task Force for Cholera Control aims to reduce cholera deaths by 90%, as outlined in "Ending Cholera: A Global Roadmap to 2030." Thus, there is optimism that transmission can be reduced and major outbreaks can be prevented.

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