Vibrio cholerae are Gram-negative rod-shaped bacteria. Only V. cholerae O-group 1 (O1) and O-group 139 (O139) cause cholera, an enteritis which can lead to massive loss of watery stools. Most of the other serogroups of V. cholerae are pathogenic as well, causing cholera-like symptoms.
After inoculation, the bacteria colonize the epithelial lining of the gut. They do not invade the bloodstream. Cholera toxin is only secreted by V. cholerae O1 and O139 and affects the small intestine.
The vast majority of infected people remain asymptomatic. Among those who develop symptoms, the majority experiences mild to moderate enteric complaints lasting a couple of days. Severe cholera appears in about 10% of infections, and is characterized by massive loss of rice-water stools, usually with vomiting and abdominal cramps. Fever is typically absent. The fluid loss can occur at a rate of 0.5 to 1 liter per hour, and leads to dehydration, electrolyte disturbances, hypovolemic shock and death within hours in the absence of timely rehydration. Severe untreated cholera has a case-fatality rate over 50%. This can be reduced to less than 1% if adequate repletion of fluid and electrolyte losses is started in time.
The incubation time is short, and ranges from 12 hours to 5 days.
Transmission mainly occurs via ingestion of fresh water in which these bacteria are found naturally or after contamination with faeces of an infected person. Ingestion of contaminated food, especially seafood, is another important transmission mode. Although less common, fecal-oral transmission via close contact with an infected individual is also possible. Cholera has a rather high infectious dose.
Risk for travellers
The risk of acquiring cholera during a tourist trip of 1 month to a low-income country is extremely low, and estimated to be less than 1 per 10 million non-immune travellers. People with low gastric acidity are more susceptible for infection and have a higher risk of developing severe symptoms after inoculation. Humanitarian aid workers have a substantial higher exposure risk, especially when working during an active outbreak in situations where sanitation is lacking, health-care facilities are poor and clean water is hard to find.
Haiti, sub-Saharan Africa, South and Southeast Asia are the main endemic regions. Cholera epidemics also occur in some other low and middle income countries, typically in impoverished areas where sanitation is insufficient and access to potable water is limited, such as slums and refugee camps.View the map
Food and water sanitation
The cornerstone of cholera prevention are good food, water, sanitation and hygiene practices. If this is maintained, the risk of acquiring cholera for travellers is exceptionally rare, even if one travels to endemic areas or regions with potential outbreaks. For people with low gastric acidity, e.g. those taking gastric acid inhibitors, the application of safe food and water hygienic measures is even more crucial. Vaccination has only limited value for travellers.
Currently, there are 3 WHO prequalified oral cholera vaccines. A first one is Dukoral®, a killed whole cell monovalent (O1) vaccine with a recombinant B subunit of cholera toxin. This inactived vaccine provides about 80 to 85% protection against cholera in the first 6 months after primary immunization. Protection is limited to infection caused by Vibrio cholerae O1, and lasts about 2 years after primary vaccination. The other two vaccines are ShanChol™ and Euvichol-Plus®, killed modified whole cell bivalent (O1 and O139) vaccines without the B subunit. These vaccines show a lower efficacy against cholera, around 65 to 70% in the first 2 years following primary vaccination. Protection lasts about 3 years. The primary vaccination schedule of all these vaccines consists of 2 oral doses.
In the US, Vaxchora® is available as a single-dose live attenuated vaccine. Vaccine efficiency against moderate to severe cholera reaches 90% by day 10 after vaccination. The duration of protection is not established yet.
There are no cholera vaccines available in Belgium. Historically, Dukoral® was used in travellers to cholera-endemic regions. However, due to restriction in vaccine indication, this vaccine has been unavailable in our country since 2021.
No country demands vaccination against cholera as an entry requirement.
Considering the low risk of acquiring the infection during stays abroad, and certainly when traveling in good hygienic circumstances, vaccination is not recommended for the vast majority of travellers. Far more important for them is the adherence to correct precautions concerning food and water safety.
Vaccination can be considered for people at increased risk of exposure and infection, in particular those who are likely to be directly exposed to cholera patients or to contaminated food or water. In this view, vaccination needs to be considered for humanitarian aid workers going to work in an area with an active outbreak. Other health care workers are generally not at special risk for cholera.