Most people exposed to the cholera bacterium (Vibrio cholerae) don't become ill and don't know they've been infected. But because they shed cholera bacteria in their stool for seven to 14 days, they can still infect others through contaminated water.

Most cases of cholera that cause symptoms cause mild or moderate diarrhea that's often hard to tell apart from diarrhea caused by other problems. Others develop more-serious signs and symptoms of cholera, usually within a few days of infection.

Symptoms of cholera infection can include:

• Diarrhea. Cholera-related diarrhea comes on suddenly and can quickly cause dangerous fluid loss — as much as a quart (about 1 liter) an hour. Diarrhea due to cholera often has a pale, milky appearance that resembles water in which rice has been rinsed.
• Nausea and vomiting. Vomiting occurs especially in the early stages of cholera and can last for hours.

• Dehydration. Dehydration can develop within hours after cholera symptoms start and range from mild to severe. A loss of 10% or more of body weight indicates severe dehydration.

  Signs and symptoms of cholera dehydration include irritability, fatigue, sunken eyes, a dry mouth, extreme thirst, dry and shriveled skin that's slow to bounce back when pinched into a fold, little or no urinating, low blood pressure, and an irregular heartbeat.

Dehydration can lead to a rapid loss of minerals in your blood that maintain the balance of fluids in your body. This is called an electrolyte imbalance.

Electrolyte imbalance

An electrolyte imbalance can lead to serious signs and symptoms such as:

• Muscle cramps. These result from the rapid loss of salts such as sodium, chloride and potassium.
• Shock. This is one of the most serious complications of dehydration. It occurs when low blood volume causes a drop in blood pressure and a drop in the amount of oxygen in your body. If untreated, severe hypovolemic shock can cause death in minutes.

The risk of cholera is slight in industrialized nations. Even in areas where it exists you're not likely to become infected if you follow food safety recommendations. Still, cases of cholera occur throughout the world. If you develop severe diarrhea after visiting an area with active cholera, see your doctor.

If you have diarrhea, especially severe diarrhea, and think you might have been exposed to cholera, seek treatment right away. Severe dehydration is a medical emergency that requires immediate care.

A bacterium called Vibrio cholerae causes cholera infection. The deadly effects of the disease are the result of a toxin the bacteria produces in the small intestine. The toxin causes the body to secrete enormous amounts of water, leading to diarrhea and a rapid loss of fluids and salts (electrolytes).

Cholera bacteria might not cause illness in all people who are exposed to them, but they still pass the bacteria in their stool, which can contaminate food and water supplies.

Contaminated water supplies are the main source of cholera infection. The bacterium can be found in:

• Surface or well water. Contaminated public wells are frequent sources of large-scale cholera outbreaks. People living in crowded conditions without adequate sanitation are especially at risk.
• Seafood. Eating raw or undercooked seafood, especially shellfish, that comes from certain places can expose you to cholera bacteria. Most recent cases of cholera in the United States have been traced to seafood from the Gulf of Mexico.
• Raw fruits and vegetables. Raw, unpeeled fruits and vegetables are a frequent source of cholera infection in areas where there's cholera. In developing countries, uncomposted manure fertilizers or irrigation water containing raw sewage can contaminate produce in the field.
• Grains. In regions where cholera is widespread, grains such as rice and millet that are contaminated after cooking and kept at room temperature for several hours can grow cholera bacteria.

Everyone is susceptible to cholera, with the exception of infants who get immunity from nursing mothers who have previously had cholera. Still, certain factors can make you more vulnerable to the disease or more likely to have 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 afflicted by famine, war or natural disasters.
• Reduced or nonexistent stomach acid. Cholera bacteria can't survive in an acidic environment, and ordinary stomach acid often serves as a 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 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 compared with people with other blood types.
• Raw or undercooked shellfish. Although industrialized nations no longer have large-scale cholera outbreaks, eating shellfish from waters known to harbor the bacteria greatly increases your risk.

Cholera can quickly become fatal. In the most severe cases, the rapid loss of large amounts of fluids and electrolytes can lead to death within hours. In less extreme situations, people who don't receive treatment can die of dehydration and shock hours to days after cholera symptoms first appear.

Although shock and severe dehydration are the worst complications of cholera, other problems can occur, such as:

• Low blood sugar (hypoglycemia). Dangerously low levels of blood sugar (glucose) — the body's main energy source — can occur when people become too ill to eat. Children are at greatest risk of this complication, which can cause seizures, unconsciousness and even death.
• Low potassium levels. People with cholera lose large quantities of minerals, including potassium, in their stools. Very low potassium levels interfere with heart and nerve function and are life-threatening.
• Kidney failure. When the kidneys lose their filtering ability, excess amounts of fluids, some electrolytes and wastes build up in the body — a potentially life-threatening condition. In people with cholera, kidney failure often accompanies shock.

Cholera is rare in the United States with the few cases related to travel outside the U.S. or to contaminated and improperly cooked seafood from the Gulf Coast waters.

If you're traveling to areas known to have cholera, your risk of contracting the disease is extremely low if you follow these precautions:

• Wash your 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.

• Drink only safe water, including bottled water or water you've boiled or disinfected yourself. Use bottled water even to brush your teeth.

  Hot beverages are generally safe, as are canned or bottled drinks, but wipe the outside before you open them. Don't add ice to your drinks unless you made it yourself using safe water.

• Eat food that's completely cooked and hot and avoid street vendor food, if possible. If you do buy a meal from a street vendor, make sure it's cooked in your presence and served hot.
• Avoid sushi, as well as raw or improperly cooked fish and seafood of any kind.
• Stick to fruits and vegetables that you can peel yourself, such as bananas, oranges and avocados. Stay away from salads and fruits that can't be peeled, such as grapes and berries.

Cholera vaccine

People traveling from the United States to areas affected by cholera can get a cholera vaccine called Vaxchora. It's suggested for people between ages 2 and 64 who plan to travel where cholera is being spread or regularly spreads. It is a liquid dose taken by mouth at least 10 days before travel.

Several other countries offer oral vaccines as well. Contact your doctor or local office of public health for more information about these vaccines. Even with the vaccine, it's important to take the above precautions to prevent cholera.

Although signs and symptoms of severe cholera can be unmistakable in areas where it's common, the only way to confirm a diagnosis is to identify the bacteria in a stool sample.

Rapid cholera dipstick tests enable doctors in remote areas to quickly confirm a cholera diagnosis. Quick confirmation helps to decrease death rates at the start of cholera outbreaks and leads to earlier public health interventions for outbreak control.

Cholera requires immediate treatment because the disease can cause death within hours.

• Rehydration. The goal is to replace lost fluids and electrolytes using a simple rehydration solution, oral rehydration salts (ORS). The oral rehydration salts (ORS) solution is available as a powder that can be made with boiled or bottled water.

  Without rehydration, approximately half the people with cholera die. With treatment, fatalities drop to less than 1%.

• Intravenous fluids. Most people with cholera can be helped by oral rehydration alone, but severely dehydrated people might also need intravenous fluids.
• Antibiotics. While not a necessary part of cholera treatment, some antibiotics can reduce cholera-related diarrhea and shorten how long it lasts in severely ill people.
• Zinc supplements. Research has shown that zinc might decrease diarrhea and shorten how long it lasts in children with cholera.

Seek immediate medical care if you develop severe diarrhea or vomiting and are in or have very recently returned from a country where cholera occurs.

If you believe you've been exposed to cholera, but your symptoms are not severe, call your family doctor. Be sure to say that you suspect your illness may be cholera.

Here's some information to help you get ready for your appointment.

When you make your appointment, ask if there are restrictions you need to follow before your visit.

Make a list of:

• Your symptoms, when they began and how severe they are
• Recent exposure to possible sources of infection, particularly if you've traveled abroad recently
• Key medical information, including other conditions for which you're being treated
• All medications, vitamins or other supplements you take, including doses
• Questions to ask your doctor

Some questions to ask your doctor about cholera include:

• Are there other possible causes for my symptoms?
• What tests do I need?
• What treatment approach do you recommend?
• How soon after I begin treatment will I begin to feel better?
• How long do you expect a full recovery to take?
• When can I return to work or school?
• Am I at risk of any long-term complications from cholera?
• Am I contagious? How can I reduce my risk of passing my illness to others?

What to expect from your doctor

Your doctor is likely to ask questions, such as:

• Have you had watery diarrhea? How severe?
• Is there anything else unusual about the appearance of your stools?
• Have you been vomiting?
• Have you experienced symptoms of dehydration, such as intense thirst, muscle cramps or fatigue?
• Have you been able to keep down any food or liquid?
• Have you recently eaten raw shellfish, such as oysters?
• Are you pregnant?
• What is your blood type, if you know?

What you can do in the meantime

Stay well hydrated. For diarrhea and vomiting that may be cholera-related, use an oral rehydration solution.

In most developing countries, you can buy powdered packets of oral rehydration salts (ORS) originally developed by the World Health Organization to treat diarrhea and dehydration in infants with cholera. Stir the powder into clean drinking or boiled water according to the package directions.

If no oral rehydration solutions are available, make your own by combining 1 quart (about 1 liter) of bottled or boiled water with 6 level teaspoons (about 30 milliliters) of table sugar and 1/2 level teaspoon (about 2.5 milliliters) of table salt.