Cholera: Symptoms, Causes & Emergency Treatment

What Is Cholera and What Causes It?

Cholera is an acute intestinal infection caused by the bacterium Vibrio cholerae. It produces a toxin that causes the intestines to release massive amounts of water, leading to severe watery diarrhea and rapid dehydration. The disease spreads through contaminated water and food, particularly in areas with poor sanitation.

Cholera has been a devastating disease throughout human history, causing seven major pandemics since 1817. Today, it remains endemic in many parts of Africa, Asia, and Latin America, and continues to cause outbreaks in areas affected by humanitarian crises, natural disasters, or inadequate water and sanitation infrastructure. The World Health Organization estimates that cholera causes 1.3 to 4 million cases and 21,000 to 143,000 deaths globally each year.

The causative agent, Vibrio cholerae, is a comma-shaped bacterium that thrives in brackish and saltwater environments. There are over 200 serogroups of V. cholerae, but only two - O1 and O139 - produce the cholera toxin responsible for epidemic disease. The O1 serogroup, which has two biotypes (classical and El Tor), causes the majority of outbreaks worldwide. The El Tor biotype, which emerged in the 1960s, now accounts for nearly all cholera cases globally and tends to cause milder illness but persists longer in the environment.

When a person ingests V. cholerae bacteria, they colonize the small intestine and produce cholera toxin (CT). This toxin binds to intestinal cells and activates an enzyme called adenylate cyclase, which causes the cells to secrete massive amounts of chloride ions. Water follows the chloride through osmosis, resulting in the profuse watery diarrhea characteristic of cholera. A person with severe cholera can lose up to 20 liters of fluid per day - explaining why dehydration can become life-threatening within hours.

How Cholera Spreads

Cholera transmission occurs through the fecal-oral route. When an infected person's feces contaminate water sources or food, others who consume these contaminated items can become infected. The bacteria can survive for extended periods in water, especially in warm, brackish environments. Common sources of infection include:

• Contaminated drinking water - The most common source of cholera outbreaks, particularly in areas without water treatment
• Ice made from unsafe water - Freezing does not kill V. cholerae bacteria
• Raw or undercooked seafood - Especially shellfish from contaminated waters, which filter and concentrate bacteria
• Uncooked fruits and vegetables - When washed or irrigated with contaminated water
• Food handled by infected persons - Poor hand hygiene can transfer bacteria to food
• Street food and food from markets - Where food safety practices may be inadequate

Person-to-person transmission is relatively rare because a large number of bacteria (typically 100 million to 1 billion organisms) are needed to cause infection in a healthy person with normal stomach acid. However, people taking acid-reducing medications, those with blood type O, or individuals who are malnourished may be more susceptible to infection with lower doses.

What Are the Symptoms of Cholera?

Cholera symptoms range from none to severe life-threatening illness. The hallmark is sudden onset of profuse, painless, watery diarrhea often described as "rice-water" stools. Severe cases develop rapid dehydration with vomiting, leg cramps, sunken eyes, rapid heart rate, and low blood pressure. Symptoms typically begin 12 hours to 5 days after infection.

The clinical presentation of cholera varies dramatically between individuals. Approximately 75-80% of people infected with Vibrio cholerae experience no symptoms or only mild diarrhea indistinguishable from other causes. However, about 20-25% develop the characteristic watery diarrhea, and of these, about half (10-20% of all infected) progress to severe, life-threatening disease requiring immediate medical intervention.

The incubation period - the time between infection and symptom onset - ranges from 12 hours to 5 days, with most people developing symptoms within 2-3 days of exposure. The onset of symptoms is typically sudden, without the prodromal period of fever and malaise seen in many other infectious diseases. Notably, cholera rarely causes fever, and abdominal pain is usually mild or absent - features that help distinguish it from other causes of acute diarrhea.

Classic "Rice-Water" Diarrhea

The characteristic diarrhea of cholera is unlike typical gastroenteritis. The stool is profuse, watery, and has a distinctive appearance resembling water in which rice has been washed - pale, slightly cloudy, with white flecks of mucus. This appearance gives rise to the classic description of "rice-water stools." The diarrhea has a characteristic fishy or slightly sweet odor due to the presence of mucus and bacteria. Importantly, the diarrhea is typically painless - patients may feel urgency but not the cramping pain associated with inflammatory diarrhea.

In severe cases, fluid loss can be staggering. Patients may pass 10-20 liters of stool per day, with some losing up to 1 liter per hour during the most acute phase. This massive fluid loss is what makes cholera so dangerous - without replacement, severe dehydration and hypovolemic shock can develop within hours.

Signs of Dehydration

As fluid loss progresses, patients develop increasingly severe signs of dehydration. Recognizing these signs is critical for determining the urgency and type of treatment needed:

Other symptoms that may accompany severe cholera include vomiting (which often follows the onset of diarrhea), muscle cramps (particularly in the legs, due to electrolyte imbalances), and weakness. Children may additionally develop hypoglycemia (low blood sugar), which can cause seizures or altered consciousness.

How Is Cholera Diagnosed?

Cholera is diagnosed through stool culture (gold standard), rapid diagnostic tests (RDTs) that provide results in 15-20 minutes, or PCR testing. In outbreak settings, clinical diagnosis based on symptoms may be sufficient to start treatment. Laboratory confirmation is important for public health surveillance and outbreak response.

In endemic areas or during outbreaks, the diagnosis of cholera is often made clinically based on the characteristic presentation of profuse watery diarrhea with rapid dehydration. The WHO case definition for suspected cholera is: in an area where cholera is not known to be present, severe dehydration or death from acute watery diarrhea in a patient 5 years or older; or in an area where there is a cholera outbreak, acute watery diarrhea with or without vomiting in a patient of any age.

However, laboratory confirmation is essential for several reasons: it confirms the diagnosis in index cases, helps distinguish cholera from other causes of acute diarrhea, enables antimicrobial susceptibility testing, and provides data for epidemiological surveillance. Several diagnostic methods are available:

Stool Culture

Stool culture remains the gold standard for cholera diagnosis. Samples should be collected before antibiotic treatment begins, as antibiotics rapidly reduce bacterial shedding. V. cholerae grows well on thiosulfate-citrate-bile salts-sucrose (TCBS) agar, where it forms characteristic yellow colonies. Culture results typically take 24-48 hours but allow for serogroup identification (O1 vs O139), biotype determination (classical vs El Tor), and antimicrobial susceptibility testing.

Rapid Diagnostic Tests (RDTs)

Rapid diagnostic tests provide results in 15-20 minutes, making them valuable for early outbreak detection and point-of-care diagnosis. These immunochromatographic tests detect V. cholerae O1 and/or O139 lipopolysaccharide antigens in stool samples. While they have lower sensitivity than culture (especially in mild cases), they offer excellent specificity and are WHO-approved for outbreak surveillance. Examples include Crystal VC and the cholera SMART test.

PCR and Molecular Methods

Polymerase chain reaction (PCR) tests can detect V. cholerae DNA with high sensitivity and specificity. PCR can identify the cholera toxin gene (ctxA), allowing differentiation of toxigenic from non-toxigenic strains. While more expensive and requiring laboratory infrastructure, PCR is increasingly used in reference laboratories and for outbreak investigation.

How Is Cholera Treated?

The cornerstone of cholera treatment is rapid fluid replacement using oral rehydration salts (ORS) solution or intravenous fluids for severe cases. This simple intervention reduces mortality from over 50% to less than 1%. Antibiotics are secondary and used only in moderate-to-severe cases to reduce duration and fluid loss. Zinc supplementation is recommended for children.

The treatment of cholera is one of the great success stories of modern medicine. Before the development of oral rehydration therapy in the 1960s and 1970s, cholera had mortality rates exceeding 50% even in hospitals. Today, with proper rehydration, mortality is less than 1% - making ORT one of the most effective medical interventions ever developed. The key principle is simple: replace the fluids and electrolytes being lost through diarrhea faster than they are being lost.

Oral Rehydration Therapy (ORT)

Oral rehydration therapy is the first-line treatment for cholera and is effective for mild to moderate dehydration. The WHO-recommended oral rehydration salts (ORS) solution contains the optimal mixture of glucose and electrolytes to maximize water absorption in the intestine. The glucose is essential because it activates sodium-glucose cotransporters in the intestinal cells, allowing sodium and water to be absorbed even while the secretory mechanism is active.

The current WHO-ORS formulation (reduced osmolarity ORS, introduced in 2004) contains per liter:

• Sodium chloride: 2.6 g
• Glucose, anhydrous: 13.5 g
• Potassium chloride: 1.5 g
• Trisodium citrate, dihydrate: 2.9 g

The solution should be prepared with clean water and given frequently in small amounts. Adults with moderate dehydration should receive 75 ml/kg over 4 hours, followed by ongoing replacement of continued losses. The solution should be used within 24 hours of preparation.

Intravenous Fluid Therapy

Patients with severe dehydration or those who cannot drink require immediate intravenous fluid therapy. Ringer's lactate solution is the preferred IV fluid because it contains lactate (which is converted to bicarbonate, helping correct acidosis) and potassium. Normal saline can be used if Ringer's lactate is unavailable but does not correct acidosis or potassium losses.

The initial goal is to restore intravascular volume rapidly. Adults with severe dehydration should receive 100 ml/kg over 3 hours (30 ml/kg in the first 30 minutes, then 70 ml/kg over 2.5 hours). Children under 1 year should receive the same amount over 6 hours. Once the patient can drink, oral rehydration should begin alongside IV therapy to replace ongoing losses.

Antibiotic Treatment

Antibiotics are not essential for cholera treatment - rehydration alone is sufficient for most cases. However, antibiotics can reduce the duration of diarrhea by 50%, decrease fluid requirements, and shorten the period of bacterial shedding. They are recommended for patients with moderate to severe dehydration. Options include:

• Doxycycline - Single 300 mg dose (adults) - first-line in most areas
• Azithromycin - Single 1 g dose (adults) or 20 mg/kg for children - used when resistance to doxycycline is suspected
• Ciprofloxacin - Single 1 g dose (adults) - alternative option

Antibiotic choice should be guided by local susceptibility patterns, as resistance is emerging in some areas. Notably, doxycycline should not be used in pregnant women or children under 8 years; azithromycin is the preferred alternative.

Zinc Supplementation

For children with cholera, zinc supplementation (20 mg/day for 10-14 days; 10 mg/day for infants under 6 months) reduces the duration and severity of diarrhea and decreases the risk of subsequent diarrheal episodes. Zinc should be given as soon as the child can eat, continuing even after diarrhea stops.

How Can You Prevent Cholera?

Cholera prevention relies on safe water, proper sanitation, food hygiene, and vaccination. The key rule for travelers is "boil it, cook it, peel it, or forget it." Oral cholera vaccines provide 65-85% protection for 2-3 years. In endemic areas, improving water and sanitation infrastructure is the long-term solution.

Preventing cholera requires a multi-faceted approach addressing water safety, sanitation, food hygiene, and vaccination. While individual protective measures are important for travelers, controlling cholera at the population level requires investment in water and sanitation infrastructure - explaining why cholera has been eliminated from high-income countries but persists in areas lacking these basic services.

Safe Water Practices

Since contaminated water is the primary source of cholera transmission, ensuring water safety is paramount. In areas where cholera is endemic or during outbreaks, only the following should be used for drinking, cooking, and brushing teeth:

• Bottled water - Ensure the seal is intact; carbonated water is generally safer
• Boiled water - Bring water to a rolling boil for at least 1 minute (3 minutes at high altitude)
• Chemically treated water - Using chlorine tablets, iodine, or household bleach (2 drops per liter)
• Filtered water - Using filters that remove bacteria (pore size 0.2-0.4 microns)

Ice should be avoided unless made from safe water. Hot beverages are generally safe if served steaming hot. Water used for hand washing should also be safe - or soap should be used, which can kill V. cholerae.

Food Safety

The classic traveler's advice "boil it, cook it, peel it, or forget it" applies especially in cholera-endemic areas. Specific recommendations include:

• Eat hot foods served hot - Food should be steaming when served
• Avoid raw seafood - Especially shellfish, which concentrate bacteria through filter-feeding
• Peel fruits and vegetables - Only eat those with intact peels that you peel yourself
• Avoid raw salads - Lettuce and other greens may harbor bacteria even after washing
• Be cautious with street food - Choose vendors with good hygiene practices and high turnover
• Avoid unpasteurized dairy - Including soft cheeses and ice cream from unknown sources

Cholera Vaccines

Several oral cholera vaccines (OCVs) are available that provide protection against cholera. The WHO currently recommends two killed whole-cell vaccines for use in endemic and epidemic settings:

• Dukoral - Contains killed V. cholerae O1 plus recombinant cholera toxin B subunit. Requires 2 doses given 1-6 weeks apart (3 doses for children 2-5 years). Provides protection for about 2 years.
• Shanchol/Euvichol - Contains killed V. cholerae O1 and O139. Requires 2 doses given 2 weeks apart. Provides protection for at least 3 years. Used in the WHO global stockpile for outbreak response.

Vaccine efficacy is 65-85% in the first year after vaccination, waning over subsequent years. Vaccination is recommended for travelers to endemic areas, humanitarian workers, and populations in outbreak settings. However, vaccines should complement, not replace, water and food safety measures.

What Complications Can Cholera Cause?

The main complications of cholera stem from severe dehydration: hypovolemic shock, acute kidney failure, electrolyte imbalances (especially low potassium), and hypoglycemia in children. With prompt rehydration, most patients recover completely without long-term effects. Without treatment, severe cholera has a mortality rate exceeding 50%.

The complications of cholera are primarily consequences of the massive fluid and electrolyte losses caused by the disease. Understanding these complications helps explain why rapid rehydration is so critical and guides monitoring and treatment of severe cases.

Hypovolemic Shock

The most immediately life-threatening complication is hypovolemic shock, which occurs when fluid loss is so severe that the circulatory system cannot maintain adequate blood pressure and tissue perfusion. Signs include rapid weak pulse, cold clammy skin, decreased consciousness, and eventually complete cardiovascular collapse. Without IV fluid resuscitation, hypovolemic shock is rapidly fatal.

Electrolyte Disturbances

Cholera diarrhea contains high concentrations of electrolytes. Potassium loss (hypokalemia) can cause muscle weakness, cramping, and potentially fatal cardiac arrhythmias. Bicarbonate loss leads to metabolic acidosis, causing rapid deep breathing as the body tries to compensate. Sodium loss contributes to hypovolemia. Proper rehydration with balanced electrolyte solutions prevents and corrects these imbalances.

Acute Kidney Injury

Severe dehydration reduces blood flow to the kidneys, leading to acute kidney injury. Patients may produce little or no urine. While usually reversible with rehydration, prolonged or severe kidney injury may require dialysis. Monitoring urine output is an important indicator of adequate fluid replacement.

Hypoglycemia

Low blood sugar is a particular concern in children with cholera. The combination of decreased food intake, vomiting, and metabolic stress can deplete glucose stores. Hypoglycemia can cause seizures, altered consciousness, and brain damage if not corrected. Children should receive glucose-containing fluids and be encouraged to eat as soon as possible.

Pregnancy Complications

Pregnant women with cholera face additional risks including fetal loss, premature labor, and complications from dehydration. However, with prompt treatment, outcomes can be good for both mother and baby. Pregnant women in endemic areas should take extra precautions to avoid exposure.

What Is the Global Impact of Cholera?

Cholera remains endemic in over 50 countries, causing 1.3-4 million cases and 21,000-143,000 deaths annually. The disease disproportionately affects impoverished populations lacking safe water and sanitation. The WHO's "Ending Cholera - A Global Roadmap to 2030" aims to reduce cholera deaths by 90% through improved water, sanitation, and vaccination programs.

Despite being preventable and treatable, cholera continues to cause significant morbidity and mortality globally. The disease serves as a stark indicator of inequity - it has been virtually eliminated from high-income countries with modern water and sanitation systems but persists where these basic services are lacking. Understanding the global epidemiology of cholera is important for travelers, healthcare providers, and public health professionals.

Cholera is currently endemic in parts of Africa, Asia, Central America, and the Caribbean. The highest burden is in sub-Saharan Africa, where approximately 40% of global cases occur. Countries experiencing conflict, displacement, or natural disasters are particularly vulnerable to outbreaks, as disruption of water and sanitation services creates conditions for transmission. Recent major outbreaks have occurred in Haiti (2010-2019), Yemen (2016-present), and various African countries.

The WHO's Global Task Force on Cholera Control (GTFCC) launched "Ending Cholera - A Global Roadmap to 2030" with the goal of reducing cholera deaths by 90% and eliminating transmission in at least 20 countries. The strategy emphasizes a multi-sectoral approach combining improved water, sanitation, and hygiene (WASH) infrastructure; oral cholera vaccination; enhanced surveillance and rapid response; and community engagement and health education.