cholera

cholera
Name	Cholera
Caption	Vibrio cholerae, the bacterium that causes the disease, as seen under a scanning electron microscope.
Field	Infectious disease
Symptoms	Profuse watery diarrhea, vomiting, muscle cramps
Complications	Dehydration, electrolyte imbalance, shock
Onset	2 hours to 5 days after exposure
Duration	Days to weeks
Causes	Vibrio cholerae spread by contaminated food or water
Risks	Poor sanitation, lack of clean drinking water, poverty
Diagnosis	Stool test
Prevention	Improved sanitation, cholera vaccines, handwashing
Treatment	Oral rehydration therapy, intravenous fluids, antibiotics
Frequency	1.3–4.0 million cases per year
Deaths	21,000–143,000 per year

cholera. Cholera is an acute diarrheal illness caused by infection of the intestine with the bacterium Vibrio cholerae. The infection is often mild or without symptoms, but can sometimes be severe and life-threatening. It is primarily spread through ingestion of water or food contaminated with the feces of an infected person, including those with no apparent symptoms.

Overview

Cholera remains a global threat to public health and an indicator of inequity and lack of social development. The disease is now endemic in many countries, particularly in regions of Africa and South Asia where access to safe water and adequate sanitation is not guaranteed. Major organizations like the World Health Organization and the Centers for Disease Control and Prevention monitor and respond to outbreaks. Historically, seven pandemics of cholera have spread from the Ganges Delta in India to much of the world.

Causes and transmission

The causative agent is the gram-negative bacterium Vibrio cholerae, with the strains of the O1 and O139 serogroups responsible for epidemics. The bacterium produces a potent enterotoxin known as cholera toxin, which triggers a massive secretion of fluids into the small intestine. Transmission occurs primarily through the fecal–oral route due to contamination of water supplies or food. Key risk factors include living in areas with inadequate wastewater treatment, as seen in crowded settings like refugee camps, and consuming undercooked seafood from contaminated waters, such as during events in Haiti following the 2010 Haiti earthquake.

Signs and symptoms

The hallmark of cholera is the sudden onset of profuse, painless, watery diarrhea often described as "rice-water" stool, which can quickly lead to severe dehydration. This is frequently accompanied by vomiting and muscle cramps caused by electrolyte losses. In severe, untreated cases, the rapid loss of body fluids can result in sunken eyes, cold skin, decreased skin elasticity, and hypovolemic shock. The progression from first liquid stool to shock can occur in as little as four to twelve hours, making the speed of intervention critical.

Diagnosis and prevention

Diagnosis is confirmed by identifying Vibrio cholerae in stool samples using techniques like dark-field microscopy or culturing on selective media such as thiosulfate–citrate–bile salts–sucrose agar. Prevention focuses on ensuring access to safe water, proper sanitation, and good hygiene practices. The World Health Organization prequalifies several effective oral cholera vaccines, including Dukoral and Shanchol, for use in endemic areas and during outbreaks. Historical figures like John Snow pioneered epidemiological methods by mapping cases in the 1854 Broad Street cholera outbreak in London, demonstrating the waterborne nature of the disease.

Treatment and prognosis

The cornerstone of treatment is rapid rehydration. Most cases can be treated successfully with prompt administration of oral rehydration salts, a solution developed by researchers at the International Centre for Diarrhoeal Disease Research, Bangladesh. Severely dehydrated patients require immediate intravenous fluids, such as Ringer's lactate. Adjunctive antibiotics, like doxycycline or azithromycin, can reduce the duration and volume of diarrhea. With timely and appropriate treatment, mortality falls below 1%; without it, the case fatality rate can exceed 50%.

Epidemiology and history

Cholera causes an estimated 1.3 to 4.0 million cases and 21,000 to 143,000 deaths worldwide each year. The seventh pandemic, caused by the El Tor biotype, began in Indonesia in 1961 and continues today. Major outbreaks have occurred in recent decades in Yemen, Zimbabwe, and Haiti. Historically, the disease shaped public health, with early pandemics reaching Europe and North America in the 19th century, leading to the development of modern epidemiology and the construction of major sewerage systems in cities like London and Chicago.

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