Typhoid fever is caused by bacteria named Salmonella typhi. A person can contract typhoid through ingesting contaminated food or drinking water. This is a highly contagious infection, and an infected person can pass the bacteria out of their body through their stool or, less commonly, through urine. When an individual develops symptoms that indicate a typhoid fever, doctors prescribe a blood test for typhoid fever diagnosis, as timely treatment is of prime importance.