Cholera

Cholera is an acute diarrhoeal disease usually associated with poverty, poor sanitation and poor access to clean drinking water Cholera

 

Key Messages

Cholera is an acute bacterial disease characterised by profuse watery diarrhoea.
Globally there are an estimated 3 – 5 million cases and 100,000 to 120,000 deaths per year.
80 percent of cases can be successfully treated with oral rehydration salts.
The majority of travellers are at low risk of disease; an effective vaccine is available for high risk groups.
Standard food, water and personal hygiene precautions should be observed.

Overview

Cholera is an acute diarrhoeal disease caused by the Gram negative bacillus Vibrio cholerae serogroup O1 or O139; humans are the only known natural hosts. V. cholerae is endemic in many low-income countries, and is usually associated with poverty, poor sanitation and poor access to clean drinking water. V. cholerae is occasionally reported in non-endemic countries, most often as a result of importation [1].

Although more than 100 serogroups exist, only two cause epidemic cholera: V. cholerae O1 (of which there are two biotypes Classical and El Tor, further divided into serotypes; Inaba, Ogawa and (rarely) Hikojima.) and V. cholerae O139, which emerged in the Bay of Bengal in 1992 and remains confined to Asia [1].

Risk areas

During 2013 cases of cholera were reported from all regions of the world, including 22 countries in Africa, 14 countries in Asia, two in Europe, eight in the Americas and one from Oceania [2]. A total of 129,064 cases of cholera including 2102 deaths were reported, giving a case-fatality rate (CFR) of 1.63%. This represents a decrease of 47% in the number of cases reported compared to 2012 and this is the second consecutive year in which reported cholera cases declined.

Worldwide trends and annual figures provided in this report exclude many cases labeled “acute watery diarrhoea”, notably occurring in south-eastern and central Asia (i.e. in Bangladesh and Pakistan) [2].

However, during outbreaks, many countries report as cholera cases many cases of acute watery diarrhoea, which are not due to Vibrio cholerae. The actual numbers of cholera cases are therefore known to differ from those reported. Differences can be explained by under-reporting due to fear of negative impact on travel and trade. Limitations in surveillance systems, inconsistencies in case definitions and lack of laboratory diagnostic capacities may also contribute to under- as well as over- reporting [2].

Risk for travellers

The overall risk of cholera for travellers is extremely low and is in the order of 0.2 cases per 100,000 travellers [3, 4]. For long-term travellers in areas of outbreaks the rate may be as high as 500 cases per 100,000 travellers [3], and when routine screening for V. cholerae is done in travellers with diarrhoea who have returned from endemic areas, the rate may approach five cases per 100,000 [5]. Activities that may predispose to infection include drinking untreated water or eating poorly cooked seafood in endemic areas. Travellers living in unsanitary conditions, for example relief workers in disaster or refugee areas, are also at risk [5].

Cholera in travellers from England and Wales

Cholera is rarely reported in UK travellers. Between 2004 and 2012, an average of 16 cases of cholera, caused by V. cholerae serogroups O1 and O139, were reported in England and Wales by the Public Health England Gastrointestinal Infections Reference Unit (Figure 2) [6].

Figure 2: Laboratory reports of Vibrio cholerae O1 and O139: England and Wales, 2004 – 2012
cholera graph
Source: Public Health England, Cholera in England and Wales: 2011-12 update

 

The Indian sub-continent is the most common region of acquisition of cholera reported in England and Wales [7]. Between 2004 and 2012, out of a total of 143 reported cases, 111 (78%) were presumed to have acquired their infection in the Indian sub-continent [Personal communication: Travel and Migrant Health Section, Public Health England, 30 May 2013].

Transmission

Cholera is transmitted via the faecal-oral route, most commonly by consumption of contaminated water and, to a lesser degree, food; direct person-to-person transmission is rare.

A high infecting dose is necessary to cause illness in healthy individuals.

Signs and symptoms

Cholera may be asymptomatic (without symptoms) or mild in healthy individuals, with diarrhoea as the only symptom [7].

The usual incubation period is 2 to 5 days, although it can be as short as several hours [7]. Severe cholera is characterised by a sudden onset of profuse, watery diarrhoea accompanied by nausea and vomiting. If left untreated, this can rapidly lead to serious dehydration, electrolyte imbalance and circulatory collapse. Over 50 percent of the most severe cases die within a few hours; with prompt, effective treatment, mortality is less than 1 percent.

Diagnosis and treatment

Health professionals should be alert to the possibility of cholera in those who have returned from endemic areas. Cholera is a notifiable disease in England and Wales. Health professionals must inform local health protection teams of suspected cases. Samples should be sent for testing (with a full clinical and travel history) to Public Health England’s Gastrointestinal bacteria reference unit (GBRU).

Rapid fluid replacement with a balanced solution of sugar, electrolytes and water (oral rehydration salts) should be started urgently and can successfully treat up to 80 percent of cases [1]. This may be done orally, but severely dehydrated cases may require intravenous administration. Cases may also be treated with antibiotics in order to improve symptoms and decrease the intestinal excretion of the organism [1]. Patients who are promptly treated should respond rapidly and recover.

Preventing cholera

For the majority of travellers advice on food and water hygiene precautions is the most appropriate prevention strategy.

An oral cholera vaccine is available in the UK. Trials of this vaccine against cholera (serotype O1) indicate that it will protect up to 86 percent of people living in cholera endemic areas for four to six months [8]. Lower levels of protection continue for three years. Protection wanes more rapidly in young children.

It has been proposed that the vaccine can be used to protect against the syndrome of travellers’ diarrhoea. While there is partial protection against one agent of travellers’ diarrhoea, Escherichia coli that produce heat labile enterotoxin, the vaccine will not protect against the many other causes of travellers’ diarrhoea [8].

Vaccine information

There is one cholera vaccine licensed for use in the UK, Dukoral™, which protects against infection caused by V. cholerae serogroup O1. It is inactivated, thiomersal-free, and does not contain live organisms, so therefore cannot cause cholera disease [9]. Each dose contains approximately 1×1011 bacteria of V. cholerae, combined with recombinant cholera toxin B [9]:

  • O1 Inaba classical biotype (heat-inactivated).
  • O1 Inaba El Tor biotype (formalin-inactivated).
  • O1 Ogawa classical biotype (heat-inactivated).
  • O1 Ogawa classical biotype (formalin-inactivated).
  • Recombinant cholera toxin B subunit (rCTB) 1 mg (produced in cholerae O1 Inaba, classical biotype).

Indications for use of vaccine

The vaccine is not indicated for most travellers, but it can be recommended for those whose activities or medical history put them at increased risk. This includes: [7-9]:

  • aid workers
  • those going to areas of cholera outbreaks who have limited access to safe water and medical care.
  • those for whom vaccination is considered potentially beneficial.

The vaccine may also provide some protection against diarrhoea caused by Escherichia coli producing a heat-labile enterotoxin. However, it is unlicensed in the UK for this use as there is limited data on efficacy in travellers; it is not recommended for this indication [9, 13]. For specific information on travellers’ diarrhoea see the separate factsheet.
 

Vaccine name and antigen component Schedule Age range
Dukoral ® cholera vaccine Two doses with an interval of at least one week between them. If more than six weeks have elapsed between doses the primary course should be restarted. A single reinforcing dose can be offered after two years. If more than two years have elapsed since the primary course, the entire course should be repeated. Adults and children older than 6 years
Dukoral ® cholera vaccine Three doses with an interval of at least one week between them. If more than six weeks have elapsed between doses the primary course should be restarted. A single reinforcing dose can be offered after six months. If more than two years have elapsed since the primary course, the entire course should be repeated. Age two to six years

Dukoral® has been given to children between 1 and 2 years of age in immunogenicity and safety studies. However, the protective efficacy has not been studied in this age group. Therefore it is not recommended for children under 2 years of age [9].

First Published :   01 Jun 2013
Last Updated :   15 May 2016

  1. Cholera Fact Sheet No 107. 2014; February. [Accessed February 2015]
  2. Weekly Epidemiological Record. Cholera, 2013; 2014; 31 (89):345-356 [Accessed February 2015]
  3. Wittlinger F, Steffen R, Watanabe H, Handszuh H. Risk of cholera among Western and Japanese travellers. J Travel Med 2:154-8, 1995.
  4. Hill DR, Ford L and Lalloo, DG. Oral cholera vaccines: use in clinical practice. Lancet Infect Dis. 6:361-73, 2006.
  5. Morger H, Steffen R, Schär M. Epidemiology of cholera in travellers, and conclusions for vaccination recommendations. BMJ. 286:184-6, 1983.
  6. Cholera in England and Wales: 2011-2012 Update. 2013; August. [Accessed February 2015]
  7. Immunisation against infectious disease. Department of Health. London. Chapter 14; Cholera. 2013; December. [Accessed February 2015]
  8. Hill DR, Ford L and Lalloo DG. Oral cholera vaccines: use in clinical practice. Lancet Infect Dis. 6:361-73, 2006
  9. Valneva UK Ltd. Summary of Product Characteristics; Dukoral. 2015; December. [Accessed December 2015]

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