Cholera

Causative agent

Cholera is an acute diarrhoeal disease caused by the bacterium Vibrio cholerae. There are many serogroups of Vibrio cholera, but only the toxigenic serogroups O1 and O139 can cause epidemic cholera.

Clinical features

Most patients do not develop any symptoms. Among those who are symptomatic, the majority have mild or moderate diarrhoea.  Others may develop severe watery diarrhoea with rice-water like stool and vomiting. Without prompt treatment, these patients may die from severe dehydration.

Mode of transmission

Cholera is usually contracted through consumption of food or water contaminated with Vibrio cholerae. Direct person-to-person transmission is rare.

Incubation period

Ranges from a few hours to 5 days, usually 2 - 3 days.

Management

The mainstay of treatment is timely and adequate rehydration. For mild dehydration, patients may take oral rehydration solution. Severe dehydration cases usually require intravenous rehydration to replenish fluid and electrolyte loss. Antibiotics may also be used if needed.

Prevention

1. Maintain good personal hygiene

• Perform hand hygiene frequently, especially before handling food or eating, and after using the toilet.
• Wash hands with liquid soap and water, and rub for at least 20 seconds; then rinse with water and dry with a disposable paper towel or hand dryer. If hand washing facilities are not available, or when hands are not visibly soiled, hand hygiene with 70 to 80% alcohol-based handrub may be considered.
• Wear gloves and a surgical mask while disposing of or handling vomitus and faeces, and wash hands thoroughly afterwards.
• Exclude infected persons and asymptomatic carriers from handling food and from providing care to children, elderly and immunocompromised people.
• Refrain from work or attending class at school, and seek medical advice if suffering from gastrointestinal symptoms such as vomiting or diarrhoea.

2. Maintain good food hygiene

• Drink only boiled water from the mains or bottled drinks from reliable sources.
• Avoid drinks with ice of unknown origin.

• Purchase fresh food from hygienic and reliable sources. Do not patronise illegal hawkers. In general, you can eat the fruit with skin after thorough washing.  However, if you would like to reduce the risk of illness especially when you travel abroad, peel raw fruit before you eat and do not eat the peelings.
• Cook all food, particularly shellfish, thoroughly before consumption.

• Susceptible populations including young children, the elderly, individuals with chronic disease and people with weakened immunity, and those who wish to reduce the risk of foodborne illnesses, should avoid consuming raw and undercooked foods.
• Adopt the 5 Keys to Food Safety in handling food, i.e. Choose (Choose safe raw materials); Clean (Keep hands and utensils clean); Separate (Separate raw and cooked food); Cook (Cook thoroughly); and Safe Temperature (Keep food at safe temperature) to prevent foodborne diseases.

Please visit the website of Centre for Food Safety for more information on food safety.

3. Maintain good environmental hygiene

• Maintain proper sanitary facilities and drainage system.
• Wear gloves and a surgical mask while cleaning and disinfecting toilets used by infected person and the soiled areas.
• Use disposable towels to wipe away all the vomitus/ faecal spillage. Then apply 1 in 49 diluted household bleach to the contaminated surfaces and the adjacent areas liberally (as a rough guide, preferably disinfect areas within 2 metres from the edge of the vomitus/ faecal spillage), especially the frequently touched surfaces e.g. door knobs, hand rail, etc. Leave for 15 – 30 minutes to allow time for the bleach to inactivate viruses; then rinse with water and keep dry. For metallic surface, disinfect with 70% alcohol.  
• Never use floor mops for cleaning up the vomitus. 
• After cleaning and disinfection, soak all cleaning tools in 1 in 49 diluted household bleach (mixing 1 part of 5.25% bleach with 49 parts of water) for 30 minutes and then rinse thoroughly and allow to air-dry before reuse. 
• Wash hands thoroughly afterwards.

Advice to travellers

• Travellers returning from affected areas should seek medical advice if they become ill. Inform the doctor of recent travel history.
• Oral cholera vaccine is rarely recommended except for those at high risk e.g. aid workers going to work in epidemic areas. It is not officially required as a condition of entry for any country. Please visit the website of Travel Health Service of the Department of Health for more details.