| 17 October 2008 |
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Typhoid Fever and Paratyphoid Fever
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Causative agents
Typhoid and paratyphoid fevers are caused by the bacteria Salmonella Typhi and Salmonella Paratyphi respectively.
Clinical features
Symptoms of typhoid fever include sustained fever, malaise, poor appetite, severe headache and vomiting. In adults, constipation is a more common symptom than diarrhoea. Enlarged spleen and liver, and rose-coloured spots on the chest are sometimes noted. It can be complicated by intestinal bleeding and perforation, impaired consciousness and even death if untreated. Occasionally, infected individuals may be asymptomatic but able to shed bacteria in their faeces or urine. Paratyphoid fever presents with similar picture, but tends to be milder.
Mode of transmission
Typhoid and paratyphoid fevers are transmitted via faecal-oral route. The causative bacteria are passed in the faeces and urine of infected people, which may contaminate food, water or beverages and cause infection in the consumer of such contaminated food. Types of food which are susceptible to contamination include shellfish (particularly oysters), raw fruits and vegetables and unpasteurised milk and dairy products.
Incubation period
Incubation period is 7-21 days.
Management
Infected individuals should seek medical attention for management. The infection can be effectively treated by antibiotics. Symptomatic treatment such as fluid replacement and adequate rest is also important. Strict personal hygiene should be observed in order to prevent transmission of bacteria to the others. The majority of patients can fully recover after treatment. However, about 2 to 5% of patients will become carriers of the bacteria and they may require long-term follow-up.
Prevention
Preventive measures are based on good personal and environmental hygiene, as well as adhesion to safe food-handling practices.
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Personal and environmental hygiene
- Wash hands properly with liquid soap and water before eating or handling food, and after going to toilet or changing diapers.
- Keep hands clean and trim fingernails regularly.
- Dispose of rubbish properly.
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Safe food-handling practices
Careful procedures of cooking and preparing food
- Drinking water should come from the mains and be boiled.
- Purchase fresh food from reliable sources. Do not patronise illegal hawkers.
- Wear a clean washable apron during food preparation.
- Clean and wash fruits and raw vegetables thoroughly before consumption.
- Scrub and rinse shellfish in clean water. Remove the viscera if appropriate.
- Cook food thoroughly and avoid raw or semi-cooked food.
- Do not handle cooked food with bare hands. Wear gloves if necessary.
- Keep the kitchen, cooking and eating utensils clean.
- Keep two sets of knife and chopping board, one for handling cooked food, another for raw food.
Hygienic food storage environment
- Consume food as soon as it is done.
- Store perishable food in refrigerator. Keep it well covered.
- Handle and store raw and cooked food, especially seafood, separately (upper compartment of the refrigerator for cooked food and lower compartment for raw food) to avoid cross contamination.
- Clean and defrost refrigerator regularly and maintain its temperature at or below 4oC.
- If necessary, refrigerate cooked leftovers and consume as soon as possible. Reheat thoroughly before consumption. Discard any spoilt food items.
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Others
- Exclude typhoid carriers from handling food and from providing care to patients.
- Immunisation for typhoid fever is not routinely recommended. It does not provide full protection from infection.
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