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Causative Agent

Vibrio cholerae 01, biotypes El Tor and classical, serotypes Inaba and Ogawa.
V. cholerae 0139, synonym Bengal (South Asia).

Incubation Period

Few hours to 5 days

Infectious Period

Throughout the duration of the illness and for a few days after clinical recovery. There is no chronic carrier state.


  • Toxigenic cholera (V. cholera 01 and 0139) are free living organisms found in fresh and brackish water often in association with copepods, shellfish and aquatic plants.
  • Infection acquired from drinking water in which V. cholera is found naturally or into which it was introduced by symptomatic or asymptomatic infected persons.
  • Contaminated fish and shellfish produce, or leftover cooked grains that have not been properly reheated.
  • Only rarely is cholera transmitted by direct person-to-person contact.


Cholera occurs sporadically in Singapore. There were 4 notified cases in 2009 compared with 7 cases in 2007 and 1 case in 2008.

In 2009, a total of 221,226 cases including 4,946 deaths, were reported in 45 countries with a fatality rate of 2.24%. Resource poor areas continue to report the vast majority of cases.

  • Most V. cholerae infections (60%) are asymptomatic.
  • Copious watery painless diarrhoea.
  • Vomiting occurs in most patients.
  • Fever and abdominal pain are uncommon.
  • Rapid progression to dehydration and acute renal failure if not treated early (<10% patients).
  • Severe cholera is characterized by acute profuse watery diarrhoea, described as “rice-water stool,” and often vomiting leading to volume depletion which if untreated may rapidly lead to hypovolaemic shock and death.

  • The diagnosis can be confirmed by isolation of the bacteria in the stool (routine stool cultures).
  • A rectal swab can be taken for culture by inserting a swab moistened in alkaline peptone water about 3 cm into the rectum. Place the swab in alkaline peptone water for transport.
  • Blood urea, electrolytes and creatinine should be measured routinely.

A legally notifiable disease in Singapore. Notify Ministry of Health (Form MD 131 or electronically via CD-LENS) not later than 24 hours from the time of diagnosis.

  • Aggressive rehydration remains the mainstay of treatment.
  • Oral rehydration for mild cases using solutions of Oral Rehydration Salts (ORS) 4 times per day and after each episode of diarrhoea.
  • In moderate to severe cases, intravenous rehydration is the treatment of choice. It is important to administer fluids containing physiological amounts of potassium and bicarbonate, and Hartman’s solution is usually recommended for this.
  • Strict monitoring of input and output (urine and stool volume) is necessary to help guide fluid therapy.
  • Correct abnormal electrolytes and acidosis.

Antibiotics shorten the duration of excretion of the V. cholerae bacteria as well as decrease the severity of the diarrhoea. The following regimens have been used:

  • Tetracycline 500 mg qds for 3 days
  • Doxycycline 300 mg single dose
  • Ciprofloxacin 1 gm single oral dose or 250mg oral daily for 3 days
  • Norfloxacin 400 mg bd for 3 days
  • Pregnant women and children: Single dose oral Azithromycin 25mg/kg up to a maximum of 1g or erythromycin 12.5 mg/kg up to a maximum of 500mg every 6 hours for 3 days (doxycycline and tetracycline are not recommended).

Cholera is spread mainly by contaminated food and water. Only rarely is there person-to-person spread. Persons with asymptomatic infection play a role in transmitting V. cholerae.

Contact precautions must be observed when handling infectious patients, i.e. wearing plastic apron if splash is anticipated and washing of hands before and after handling patients, as well as proper disposal of stools and vomitus and decontamination of instruments after use on patient.

A modified killed whole-cell oral vaccine (containing 01 and 0139 serotypes) showed promise as a safe, effective, and affordable vaccine for endemic regions in a cluster-randomized, double-blind, placebo-controlled phase 3 trial. However, durability of protection is yet to be established.

Three components of public health have largely prevented outbreaks of cholera in Singapore:

  • Hygienic disposal of human waste
  • An adequate supply of safe drinking water
  • Good food hygiene.

In the event of an outbreak:

  • All acute cases and carriers will be isolated and treated at the Communicable Disease Centre (CDC) at Tan Tock Seng Hospital.
  • Contacts and implicated food handlers with or without diarrhoea will be screened for cholera infection at the CDC.
  • Epidemiological investigations will be carried out by the Communicable Diseases Division, MOH to trace the source of infection.
  • Closure of implicated food outlets will be initiated if necessary.
  • Any outbreak will be notified to the public as well as the WHO.

Two oral cholera vaccines which provide higher level protection (85%) against V. cholerae 01 have recently become available in a few countries. One  vaccine contains genetically-engineered live attenuated Vibrio cholerae 01 strain (CVD 103 HgR) and the other contains inactivated Vibrio cholerae 01 plus the B subunit of cholera toxin. The latter (Dukoral, Aventis Pharma) is now registered in Singapore.

The risk of cholera for general travellers is very small. Cholera vaccine for travellers is only indicated for those travelling > 1 month in cholera endemic areas and for refugee/aid workers in countries with cholera.

No vaccine is available against V. cholerae 0139.


  1. Sur D, Lopez AL, Kanungo S et al. Efficacy and safety of a modified killed-whole-cell oral cholera vaccine in India: an interim analysis of a cluster-randomised, double-blind, placebo-controlled trial. Lancet. 2009;374:1694-702.
  2. WHO. Cholera update 2009. Weekly Epidemiological Record 2010;85:293-308.
  3. WHO. Cholera vaccine. Weekly Epidemiological Record 2010;85:117-28.
  4. Wong CS, Ang LW, James L et al. Epidemiological characteristics of cholera in Singapore, 1992- 2007. Ann Acad Med Singapore 2010;39:507-12.

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