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11 August 2017
Typhoid Fever and Paratyphoid Fever  

Causative agents

Typhoid and paratyphoid fevers are caused by the bacteria Salmonella Typhi and Salmonella Paratyphi respectively.

Clinical features

Typhoid fever is an infection that can spread throughout the body and affect many organs. Symptoms of typhoid fever include sustained fever, headache, malaise, loss of appetite, and constipation or diarrhoea (adults tend to get constipation while children tend to get diarrhoea). In some cases, enlarged spleen and liver are seen, and rose-coloured spots appear on the chest, abdomen and back. In severe cases, there may be 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

For typhoid fever, the incubation period is usually 7 – 21 days. The incubation period for paratyphoid fever is usually 1 – 10 days.

Management

Infected individuals should seek medical advice 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 – 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.

  1. Personal and environmental hygiene
    • Wash hands properly with liquid soap and water before handling food, after handling raw meat or poultry and before eating, and after going to toilet or changing diapers
       
    • Keep hands clean and trim fingernails regularly
       
    • Dispose of rubbish properly
       
  2. Safe food-handling practices: 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
     
    • Careful procedures of cooking and preparing food
       
    • Drinking water should come from the mains and be boiled
       
    • Avoid using ice in drinks if its source or the hygienic condition of the food premises is doubtful
       
    • Bottled or prepackaged beverages are usually safe to drink, but remember to wipe clean and dry the packaging before opening
       
    • Patronise reliable and hygienic shops and avoid buying food from street vendors or food outlets with poor environmental hygiene condition or seen to have improper food handling
       
    • Wash fruits and vegetables under clean running water and avoid those with damaged skin
       
    • Scrub and rinse shellfish in clean water. Remove the viscera before cooking, if applicable
       
    • Cook food thoroughly and avoid raw or undercooked food
       
    • Keep the kitchen, cooking and eating utensils clean
       
    • Use separate utensils (e.g. knife and chopping board) to handle raw food and cooked food or ready-to-eat food
       
    • Hygienic food storage environment
       
    • Take food promptly after cooking. Perishable foods that has been kept at room temperature for more than 4 hours should be discarded
       
    • Choose ready-to-eat, cooked or perishable foods that are stored correctly, e.g. hot food at above 60°C, cold food at or below 4°C, frozen food at or below -18°C
       
    • If perishable food is not consumed immediately, keep it at 4°C or below. Keep it well covered
       
    • Handle and store raw and cooked food separately. Store raw meat, poultry, and seafood below ready-to-eat food or cooked food in the fridge to prevent juices from dripping onto ready-to-eat food or cooked food
       
    • Clean and defrost refrigerator regularly. Check the temperature of the refrigerator with a thermometer and ensure the fridge is kept at or below 4°C and freezer at or below -18°C
       
    • If necessary, refrigerate cooked leftovers and consume as soon as possible. Reheat thoroughly before consumption. Discard any spoilt food items

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

  1. Others
     
    • Exclude typhoid carriers from handling food and from providing care to patients
       
    • Immunisation for typhoid fever is not routinely recommended. Even vaccinated individuals should take care to avoid consumption of potentially contaminated food and water as the vaccine does not provide full protection from infection
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