Cholera Signs and Symptoms
Cholera is an acute, diarrheal illness caused by infection of the intestine with the bacterium Vibrio cholerae. An estimated 3-5 million cases and over 100,000 deaths occur each year around the world. The infection is often mild or without symptoms, but can sometimes be severe. Approximately one in 20 (5%) infected persons will have severe disease characterized by profuse watery diarrhea, vomiting, and leg cramps.
In these people, rapid loss of body fluids leads to dehydration and shock. Without treatment, death can occur within hours. The cholera bacterium is usually found in water or food sources that have been contaminated by feces from a person infected with cholera. Cholera is most likely to be found and spread in places with inadequate water treatment, poor sanitation, and inadequate hygiene.
The cholera bacterium may also live in the environment in brackish rivers and coastal waters. Shellfish eaten raw have been a source of cholera, and a few persons in the U.S. have contracted cholera after eating raw or undercooked shellfish from the Gulf of Mexico
Epidemiology of Cholera
Cholera affects an estimated number of about 3-5 million people worldwide, and causes 58,000-130,000 deaths a year as 2010. This occurs mainly in the developing world. In the early 1980s, death rates are believed to have been greater than 3 million a year. It is difficult to calculate exact numbers of cases as may go unreported due to concerns that an outbreak may have a negative impact on the tourism of a country. Cholera remains both epidemic and endemic in many areas of the world.
Although much is known about the mechanisms behind the spread of cholera. This has not lead to a full understanding of what makes cholera outbreaks happens some places and not others. Lack of treatment of human feces and lack of treatment of drinking water greatly facilitates its spread, but bodies of water can serve as a reservoir and sea food shipped long distances can spread the disease. Cholera was not known in the Americans for most of the 20th century, but it spread towards the end of that century.
Signs and Symptoms of Cholera
Cholera infection is often mild or without symptoms, but can sometimes be severe. Approximately one in 20 (5%) infected persons will have severe disease characterized by profuse watery diarrhea, vomiting, and leg cramps. In these people, rapid loss of body fluids leads to dehydration and shock. Without treatment, death can occur within hours.
The primary symptoms of cholera are profuse diarrhea and vomiting of clear fluid. These symptoms usually start suddenly, half a day to five days after ingestion of the bacteria. An untreated person with cholera may produce 10 to 20 litres of diarrhea a day. Severe cholera kills about half of affected individuals. Estimates of the ratio of asymptomatic to symptomatic infections have ranged from 3 to 100. Cholera has been nicknamed the "blue death" because a victim's skin turns bluish-gray from extreme loss of fluid.
If the severe diarrhea is not treated, it can result in life-threatening dehydration and electrolyte imbalances.
Fever is rare and should raise suspicion for secondary infection. Patients can be lethargic, and might have sunken eyes, dry mouth, cold clammy skin, decreased skin turgor, or wrinkled hands and feet. Kussmaul breathing, a deep and labored breathing pattern, can occur because of acidosis from stool bicarbonate losses and lactic acidosis associated with poor perfusion. Blood pressure drops due to dehydration, peripheral pulse is rapid and thready, and urine output decreases with time. Muscle cramping and weakness, altered consciousness, seizures, or even coma due to electrolyte losses and ion shifts are common, especially in children.
Dry mucus membranes or mouth
Glassy or sunken eyes
Lack of tears
Low urine output
Rapid pulse (heart rate)
Sunken "soft spots" (fontanelles) in infants
Unusual sleepiness or tiredness
Watery diarrhea that starts suddenly and has a "fishy" odor
Note: Symptoms can vary from mild to severe.
Diagnosis of Cholera
It is almost impossible to distinguish a single patient with cholera from a patient infected by another pathogen that causes acute watery diarrhea without testing a stool sample.
A review of clinical features of multiple patients who are part of a suspected outbreak of acute watery diarrhea can be helpful an identifying cholera because of the rapid spread of the disease.
While management of patients with acute watery diarrhea is similar regardless of the illness, it is important to identify cholera because of the potential for a wide spread outbreak.
How to Diagnose
Isolation and identification of Vibrio cholerae serogroup O1 or O139 by culture of a stool specimen remains the gold standard for the laboratory diagnosis of cholera.
Cary Blair media is ideal for transport, and the selective thiosulfate–citrate–bile salts agar (TCBS) is ideal for isolation and identification.
Reagents for serogrouping Vibrio cholerae isolates are available in all state health department laboratories in the U.S. Commercially available rapid test kits are useful in epidemic settings but do not yield an isolate for antimicrobial susceptibility testing and subtyping, and should not be used for routine diagnosis.
Rapid Tests for Cholera
In areas with limited to no laboratory testing, the Crystal VC® dipstick rapid test can provide an early warning to public health officials that an outbreak of cholera is occurring. However, the sensitivity and specificity of this test is not optimal.
Therefore, it is recommended that fecal specimens that test positive for V. cholerae O1 and/or O139 by the Crystal VC® dipstick be confirmed using traditional culture-based methods suitable for the isolation and identification of V. cholerae.