Typhoid fever is a life-threatening disease of the intestinal system caused by the typhoid bacillus, Salmonella typhosa, which lives only in humans who carry it in their bloodstream and intestinal tract. Typhoid fever is spread when the bacteria is "shed" by infected people who handle food or fluids without washing their hands, or when sewage carrying the bacteria contaminates water, milk, and other foods. Although relatively rare since the advent of vaccines and improvement of public sanitation (about 400 cases are reported annually in the United States, 70% of which are acquired through international travel), typhoid fever was once common and still arises in impoverished areas of the world where squalid conditions prevail and medical treatment is unavailable. Symptoms of the disease become evident within one to two weeks after infection and include sore throat, fever, headache, nausea, and loss of appetite, which are sometimes followed by the...