Cause of typhoid fever

Learn about the cause of typhoid fever and how it is spread.

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The cause of typhoid fever

Typhoid fever is an illness caused by a type of Salmonella bacteria called Salmonella typhi.

How typhoid fever is spread

Typhoid fever is spread when you drink water or eat food that has been contaminated with the bacteria, such as:

  • milk and milk products
  • shellfish from areas polluted with sewage
  • raw fruits and vegetables grown in soil fertilized with human feces

It can also be spread if you come into contact with the feces of an infected person.

You can continue to infect others even after you stop experiencing symptoms. Some people continue to spread the bacteria after recovery. These people are called carriers because they are infected but no longer feel sick.

How food and water become contaminated

Water can become contaminated with the Salmonella typhi bacteria when feces from infected people, including carriers, enter the water supply. Food can then become contaminated when this water is used on crops or in food processing and packaging.

Food can also become contaminated when an infected person, including a carrier, prepares food without properly washing their hands.

Where typhoid fever is found

The bacteria that cause typhoid fever are common in developing countries with poor sanitation and low standards of hygiene. It can be found in sewage and untreated water in high-risk areas.

In Canada, most cases result from travel to high-risk areas.

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