Diseases caused by Salmonella ssp. Typhoid fever is caused by Salmonella typhi. This is a rare infection in the US but very common around the world. The bacterium is restricted to humans, and the severity and duration of the disease depend on how many bacteria are ingested, the virulence of the strain, and the relative health of the individual. The bug grows in the gut and causes fever, headache, cramps and diarrhea.
Most people recover.
In other cases, the organism invades macrophages and can become septicemic. Occasionally, the bug hides in the gall bladder and becomes latent. Here the patient has no symptoms but sheds infectious organisms for years. This is cause by S. typhimurium. The organism resides in a variety of animals, especially fowl.