Cholera may not be a major concern for most Americans but it is one of the main diarrheal illnesses that causes over 100,000 deaths per year throughout the world. It had been almost totally eliminated in the United States with the last local outbreak being in 1911. But in recent years, especially after Hurricanes Rita and Katrina, there has been greater awareness about the dangers of cholera.

With only about 10 cases of cholera occurring in the United States every year, it may not pose a major health threat to most Americans. People traveling to endemic areas obviously need to be cautious especially when it comes to food and water. For Americans who do not travel across the border, cholera can still be a risk when consuming seafood that is undercooked, like raw oysters and sushi. Even with seafood sourced from the US or imported fruit and vegetables.

Understanding cholera, the disease and the dangers, whether it is contracted locally or abroad can ultimately be a life and death situation. Up to half of all untreated cholera cases are fatal yet this could be avoided. The fact of the matter is that cholera is easily treatable. In fact it is not the cholera infection itself that is the killer but rather the complications that can be fatal. Dehydration in cholera can develop so fast and be so severe that it can kill an infected person within just a few days.

Cholera is caused by toxins

Cholera is a disease affecting mainly the small intestine. It is caused by a bacterium known as Vibrio cholerae which is a tiny comma-shaped microbe. Contrary to popular belief, cholera does not only exist in dirty water. The bacteria are so small that it can exist in the millions within a glass of water that looks otherwise clean and clear. The bacteria is less than 60 times the size of a grain of very fine sand. Cholera bacteria act by producing certain toxins known as CTX.

These toxins irritate the wall of the bowels causing copious amounts of water to empty into the lumen of the small intestine. Even though the colon reabsorbs most water from the stool and is not usually prone to the cholera toxin, the sheer amount of water that may be present from the small intestine cannot be reabsorbed by the colon. This gives rise to the characteristic very watery stool seen in cholera.

Dangerous cholera strains


Cholera bacteria are comma-shaped and less
than 1/60th the size of a grain of fine sand.

There are several different strains of Vibrio cholerae, the bacterium that cause cholera. Some are considered pathogenic meaning that it can cause disease, and others are non-pathogenic in that it may not cause a disease in humans. In fact there are over 200 types of cholera bacteria that have been identified. The two types that are most likely to cause severe disease in humans and the main ones responsible for epidemics are V.cholerae O1 and O139. From these two types, it is O1 that is the most common disease-causing cholera strain.

Watery ‘rice milk’ diarrhea

Cholera is a diarrheal illness. This means that the main symptom is diarrhea and vomiting is also common and severe. But it is not just the regular diarrhea that many of us experience every now and then. Cholera diarrhea is among the worst type of infectious diarrhea that you will ever experience when compared to the regular stomach flu (viral gastroenteritis) and other tummy bugs. The hallmark of cholera is profuse watery diarrhea to such an extent that a person can lose up to one liter of water an hour in the stool.

cholera_diarrhea
Typical cholera stool looks like rice-water.

The diarrhea also has a characteristic fishy odor. The pale colored to white diarrhea is commonly known as a rice-water or rice-milk diarrhea. It is similar to the water that is formed after boiling rice. Although there may be no blood or mucus visible in the stool, the degree to which the bowels are irritated can be severe. It is not just water that is lost in cholera diarrhea. Large amounts of electrolytes like sodium and chloride are lost along with the watery stool.

Cholera is not contagious

A contagious disease is one that can easily be spread from person to person. Cholera is not contagious meaning that chance of being transmitted from one person to another through direct contact is highly unlikely. The bacteria needs to be consumed in large quantities through contaminated food or water. It takes about 10 million cholera bacteria to cause the disease although smaller numbers may still be dangerous if it can survive the passage through the stomach.

Cholera_bacteria
It takes between 1,000 to 10 million
cholera bacteria to cause the disease.

Given the large number of bacteria needed to enter the gut in order to cause cholera, touching a person who has the disease, objects that they have touched or even contaminated food or water may not cause the disease. Nevertheless practicing good hygiene by washing the hands throughly and using an antiseptic handwash is essential, if not to avoid cholera then at least other infections. It is possible that consuming water with as little as 1,000 bacteria or food with just 100 bacteria will be sufficient to cause diarrhea.

Cholera is everywhere

Although cholera causes major outbreaks in developing nations, especially areas hit with poverty, natural disasters and wars, the bacteria is present throughout the world. It is found naturally in coastal waters often attached to copepods, tiny crustaceans that feed of algae and plankton. When consumed by humans through contaminated food or water, the bacteria is then passed out in the stool. Should the feces from an infected human then contaminate a water source, the bacteria can quickly spread not only through drinking water but also through raw foods.

It is often thought that cholera only exists in developing nations. While it is true that there are ongoing cholera pandemics in Africa, Asia and Latin America, an outbreak could even occur in the United States. Proper sanitation and treatment of drinking water makes this unlikely but not impossible. Certain pathogenic strains of cholera have become indigenous to the Gulf Coast of the United States. In 2005, there was a spike in infections in Louisiana after Hurricanes Katrina and Rita, when people ate partially cooked seafood.

Danger with sushi and other foods

sushi
Sushi, sashimi and raw oysters
can contain cholera bacteria.

The risk of contracting cholera through contaminated water in the United States is highly unlikely given the proper sanitation and water treatment standards. However, the risk still exists with consuming seafood in particular. Eating raw oysters and sushi or sashimi made with contaminated fish can lead to cholera. These contaminated seafoods may not necessarily be imported from foreign nations where cholera is endemic. In fact, eating improperly cooked seafood sourced from the Gulf Coast waters may hold a major cholera risk these days.

But cholera is not restricted to just seafood and water. Vegetables and fruits that may be irrigated with contaminated water can harbor the bacteria. If eaten raw, vegetables and unpeeled fruits can be just as dangerous. Imported vegetables and fruits need to be sourced carefully as not every country has high standards with regards to clean irrigation water. Cleaning, cooking and peeling fruits and vegetables can reduce the risk.

Stomach acid drugs kills cholera

Most of the cholera bacteria are destroyed in the stomach. These bacteria are not acid resistant. The strong stomach acid and digestive enzymes can easily kill the bacteria and prevent the disease. Therefore large numbers of cholera bacteria have to be consumed to cause the disease. At least some of these bacteria may survive the passage through the stomach to then reach the small intestine, multiply to large numbers and cause cholera. However, these days there is the problem of normal stomach acid being hampered by modern drugs.

Gastroesophageal reflux disease (acid reflux), gastritis and peptic ulcer disease (PUD) are the most common upper gastrointestinal problems seen throughout the world these days. It is widely treated with antacids and acid-suppressing drugs like proton pump inhibitors (PPIs).  In fact these drugs are available over-the-counter without a prescription and are often misued. The danger with using these drugs in terms of cholera is that it reduces the quantity of the stomach acid or makes it less acidic thereby compromising the natural defenses against the cholera bacteria.

References :

www.who.int/mediacentre/factsheets/fs107/en/index.html

www.cdc.gov/cholera/epi.html

emedicine.medscape.com/article/962643-overview

www.mayoclinic.com/health/cholera/DS00579

 


Article reviewed by Dr. Greg. Last updated on January 21, 2013