Vibrio cholerae (V. cholerae) is a species of Gram-negative facultatively anaerobic bacteria of curved rod-shaped with single polar flagella. V. Cholerae has been classified into approximately 200 serogroups. Strains belonging to serogroups O1 and O139 cause the vast majority of cholera cases (1).
Vibrio cholerae is found naturally in brackish riverine, estuarine, and coastal waters. Recognized hosts of the organism include algae, shellfish, chironomid egg masses, fish, waterfowl, amebae, and copepods (2). V. cholerae colonies can form biofilms on both biotic and abiotic surfaces – including on shells, zooplankton, macroalgae, ship hulls, and plastic pollution (3-5).
Cholera Transmission and Disease Severity
Cholera is primarily transmitted through the consumption of fecally contaminated water and food. Foodborne outbreaks are most frequently linked to fish, shellfish, crabs, oysters, clams, rice, millet gruel, and vegetables (6).
Most V. cholerae infections are asymptomatic or mild in nature. Individuals with asymptomatic infections may still shed bacteria in their feces and infect others (7). Approximately 10% of V. cholerae infections will progress to severe disease (8). In endemic settings, the most severe infections occur in children, while in epidemic settings, severe disease occurs in adults as frequently as it does in children (9).
Individuals with blood type O are more likely to suffer from severe V. cholerae infection (10). The use of drugs that reduce stomach acid, such as antacids, histamine receptor blockers, and proton pump inhibitors, also increases the risk of severe infection (11).
Signs and Symptoms of Cholera
Cholera has an average incubation period of 1-5 days. Patients will experience a sudden onset of painless, watery diarrhea that may be accompanied by vomiting. The diarrhea is often characterized as having a “rice water” appearance and fishy odor. Fever is uncommon in adults, but often present in children (12).
In severe cases, dehydration may lead to the rapid progression to acidosis and electrolyte imbalance. Coma may occur. Without the replacement of fluids and electrolytes, hypovolemic shock and death ensue (12).
If left untreated, cholera has a 25-50% mortality rate. Proper treatment reduces the mortality rate to less than 1% (13).
Diagnosis and Treatment of Cholera
Cholera is diagnosed via stool culture. When a case is suspected, healthcare and medical laboratory personnel should follow stool precautions.
Mild and moderate cases of cholera can be successfully treated with oral rehydration salts, while severe cases require rehydration with intravenous fluids (14). The World Health Organization (WHO) recommends reserving antibiotics as a treatment for severe cases only, as antibiotic use has no proven effect on controlling the spread of the disease and may contribute to antimicrobial resistance (15). In severe cases, tetracycline, doxycycline, azithromycin, erythromycin, or ciprofloxacin may be used (12). Most people who recover from V. cholerae infection incur long-lasting immunity (16).
Cholera originated in India and spread across the world during the 19th century (17). Since that time, there have been seven cholera pandemics, including one that is ongoing today (18).
Currently, approximately 1.3 billion people are at risk for cholera in endemic countries. An estimated 2.86 million cholera cases occur annually, resulting in an estimated 95,000 deaths (19).
Over the last decade, the countries reporting the most cases of cholera have included Yemen, Somalia, the Democratic Republic of Congo, Mozambique, Bangladesh, and Haiti. If you have a GIDEON account, click here to explore the Cholera outbreak map. Cholera is exceedingly rare in Europe and the United States.
Cholera cases by region, 1953 – 2018
When traveling to an area where cholera is endemic, precautions should include adherence to proper hand hygiene, drinking only bottled water, and avoiding uncooked food.
Ongoing worldwide efforts to end the current cholera pandemic center on increasing access to clean water and sanitation and expanding accessibility to existing cholera vaccines.
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