TYPHOID FEVER

Typhoid fever is a foodborne illness, caused by one species of Salmonella bacteria. Salmonella bacteria are often a cause of food poisoning, however in the case of typhoid fever, the Salmonella typhi bacteria can cause a more serious illness.

The onset of typhoid fever is normally gradual, with fever, malaise, chills, headache, and generalized muscle and joint aches. Infection may also cause the spleen to enlarge, the white blood cell count to drop, and small rose-coloured spots to develop on the trunk. Diarrhea occurs infrequently. Vomiting may occur late in the first week following infection, but is usually not severe.

Diagnosis of typhoid fever is made by laboratory tests to detect the presence of Salmonella typhi from a blood or stool sample.

Typhoid fever can be effectively treated using antibiotics. The usual case-fatality rate of 10% can be reduced to less than 1% if prompt antibiotic treatment is given. Relapses can occur following treatment.

Like other Salmonella species, Salmonella typhi is transmitted by contaminated food and water. The bacteria is found in many developing countries of Latin America, Africa, and Asia. It can contaminate shellfish (particularly oysters), raw fruits and vegetables, and raw milk.

Travellers to countries with inadequate water and sewage treatment are at risk of acquiring typhoid and should take precautions to avoid consumption of potentially contaminated food and water. Drinking only boiled water or carbonated beverages and eating only cooked food, lowers the risk of infection. There are vaccines available which have been shown to give 70-90% protection to those vaccinated. Vaccination may be recommended for long-stay travellers to developing countries or for those international travellers with pre-existing health conditions that may increase their susceptibility.

In Canada, as in other developed countries with modern water and sewage treatment facilities and pasteurized milk, typhoid fever has now become rare. Less than 100 cases per year have been reported in Canada during the last 10 years. Occasional cases occur in international travellers, especially those arriving from developing countries, but these isolated cases do not pose a risk of spread within Canada because water and sewage is treated to kill bacteria. There is no need for routine vaccination against typhoid of any persons who deal with international travellers, as the disease is not transmitted directly from person to person.