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Infectious Disease and Microbiology – Cholera
Cholera is a severe watery diarrheal illness caused by Vibrio cholerae. It is characterized by rapid fluid loss that can lead to life-threatening dehydration if untreated.
Globally, cholera remains a major public health problem, with an estimated 3–5 million cases and 100,000–120,000 deaths annually. It is one of the leading causes of death in children under five years of age worldwide. The disease is most common in areas with poor sanitation, contaminated water supplies, and during humanitarian crises or natural disasters.
Risk factors include exposure in endemic or epidemic settings, malnutrition, and immunosuppression, which may lead to a more severe clinical course. Individuals with blood group O are at increased risk of severe disease, particularly with the El Tor subtype. In pregnancy, cholera increases the risk of miscarriage or premature delivery, especially in the third trimester.
Transmission occurs through the fecal–oral route, typically via contaminated water, food, or undercooked seafood. The incubation period ranges from 12 hours to 5 days but may be as short as a few hours in cases of high bacterial inoculum or reduced gastric acidity. The organism produces cholera toxin, which consists of one A subunit and five B subunits. The toxin binds to enterocytes in the small intestine and stimulates chloride ion secretion, resulting in massive water loss into the intestinal lumen.
Vibrio cholerae is a gram-negative rod with over 190 serotypes based on the O antigen. Only serogroups O1 (El Tor and classical biotypes) and O139 are responsible for epidemic cholera. Non-O strains typically cause milder diarrheal illness.
Clinically, cholera presents with sudden onset of profuse watery diarrhea, often described as “rice water stools” with a fishy odor. Stool output can exceed one liter per hour in severe cases (cholera gravis). Patients may experience abdominal cramping but typically do not have fever. Vomiting may occur. Signs of dehydration include poor skin turgor, dry mucous membranes, tachycardia, hypotension, and in severe cases, shock.
Initial laboratory evaluation includes assessment of electrolytes, glucose, and renal function. Severe dehydration may lead to metabolic acidosis, hypokalemia, and acute kidney injury. Diagnosis can be confirmed by stool culture using selective media such as thiosulfate citrate bile sucrose (TCBS) agar. Gram stain may reveal motile gram-negative rods. However, treatment should not be delayed while awaiting confirmation.
The cornerstone of therapy is prompt and aggressive rehydration. Oral rehydration solution (ORS) is highly effective because sodium and glucose absorption remain intact despite toxin activity. Approximately 80% of patients recover with oral hydration alone. Intravenous fluids, preferably isotonic solutions such as lactated Ringer’s, are indicated in patients with severe dehydration or inability to tolerate oral intake.
Antibiotics are adjunctive to rehydration and reduce stool volume by approximately 50% and shorten the duration of bacterial shedding. First-line options include tetracycline (500 mg orally four times daily for 3 days) or a single 300 mg dose of doxycycline. Alternative agents include azithromycin, ciprofloxacin, or norfloxacin. In children and pregnant women, erythromycin or azithromycin is preferred; quinolones and tetracyclines should be avoided in these groups.
Zinc supplementation (30 mg daily) has been shown to decrease stool output and duration of illness, particularly in children. Close monitoring of electrolyte status, acid–base balance, glucose levels, and volume status is essential. Hospital admission is indicated for severe dehydration, inability to tolerate oral fluids, or signs of shock.
Preventive measures include safe water practices such as boiling, chlorination, filtration, and strict hand hygiene. Vaccination with killed whole-cell oral vaccines is recommended by the World Health Organization in endemic areas and provides approximately 78% protection for up to two years. Herd immunity significantly reduces transmission, and partial population vaccination can substantially lower case numbers.
Prognosis is excellent with timely rehydration. However, untreated cholera carries a mortality rate of up to 50%. Complications include arrhythmias due to electrolyte disturbances and acute renal failure secondary to severe dehydration.
Rapid recognition of acute watery diarrhea and immediate initiation of rehydration are critical. Management should focus on fluid and electrolyte replacement first, with antimicrobial therapy administered once the patient is stabilized. Suspected cases should be reported promptly to public health authorities to prevent outbreaks.
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