Cholera

Intestinal infection due to Vibrio cholerae

Cholera is a potentially epidemic and life-threatening infection of the intestine, characterised by extreme watery (secretory) diarrhoea often accompanied by vomiting, with rapid depletion of body fluids and salt that may result in hypovolemic shock and acidosis. Cholera outbreaks are caused by toxigenic strains of Vibrio cholerae serogroups O1 and O139. Serogroup O1 has two biovars; classical and eltor. Vibrio cholerae O1, biovar cholerae is classical type. Vibrio cholerae O1, biovar eltor is eltor type.

Symptoms (Clinical manifestations)

Cholera is an extremely virulent disease transmitted through the ingestion of contaminated food or water (2). Cholera can cause severe acute watery diarrhoea and the severe forms of the disease can kill within hours if left untreated.

Most people infected with V. cholerae do not develop any symptoms, although the bacteria are present in their faeces for 1–10 days after infection and are shed back into the environment, potentially infecting other people.

Among people who develop symptoms, the majority have mild or moderate symptoms. It takes between 12 hours and 5 days for a person to show symptoms. A minority of patients develop acute watery diarrhoea with severe dehydration. This can lead to death if left untreated.

Watery 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.

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.

Diagnostics

A rapid dipstick test is available to determine the presence of V. cholerae. In those samples that test positive, further testing should be done to determine antibiotic resistance.In epidemic situations, a clinical diagnosis may be made by taking a patient history and doing a brief examination. Treatment via hydration and over-the-counter hydration solutions can be started without or before confirmation by laboratory analysis, especially where cholera is a common problem.

Stool and swab samples collected in the acute stage of the disease, before antibiotics have been administered, are the most useful specimens for laboratory diagnosis. If an epidemic of cholera is suspected, the most common causative agent is V. cholerae O1. If V. cholerae serogroup O1 is not isolated, the laboratory should test for V. cholerae O139. However, if neither of these organisms is isolated, it is necessary to send stool specimens to a reference laboratory.[citation needed]

Infection with V. cholerae O139 should be reported and handled in the same manner as that caused by V. cholerae O1. The associated diarrheal illness should be referred to as cholera and must be reported in the United States.

Treatment

Cholera is an easily treatable disease. The majority of people can be treated successfully through prompt administration of oral rehydration solution (ORS). The WHO/UNICEF ORS standard sachet is dissolved in 1 litre (L) of clean water. Adult patients may require up to 6 L of ORS to treat moderate dehydration on the first day. Severely dehydrated patients are at risk of shock and require the rapid administration of intravenous fluids. These patients are also given appropriate antibiotics to diminish the duration of diarrhoea, reduce the volume of rehydration fluids needed, and shorten the amount and duration of V. cholerae excretion in their stool. All patients should begin to eat safely prepared, regular local food as soon as they can safely do so. Breastfeeding should also be promoted. Rapid access to treatment is essential during a cholera outbreak. Oral rehydration should be available in communities, including at specific oral rehydration points (ORPs), in addition to larger treatment centres that can provide intravenous fluids and 24-hour care. With early and proper treatment, the case fatality rate should remain below 1%. Zinc is an important adjunctive therapy for children under 5, which also reduces the duration of diarrhoea and may prevent future episodes of other causes of acute watery diarrhoea. Mass administration of antibiotics is not recommended, as it has no proven effect on the spread of cholera and may contribute to antimicrobial resistance.