Paratyphoid fever pathophysiology

Overview
It starts when the bacterium Salmonella typhi is passed from another person due to bad hygiene such as lack of washing hands after using the restroom. Eventually the bacteria passes down to bowel, then penetrating the intestinal mucosa (lining) to the underlying tissue. If the immune system is unable to stop the infection here, bacteria multiplies and spread to the bloodstream, after which the first signs of disease are observed in the form of fever. Bacteria can penetrate further to the bone marrow, liver and bile ducts, and are excreted into the bowel contents.

In the second phase of the disease, bacteria penetrates the immune tissue of the small intestine, and the initial symptoms of small-bowel movements begin

Mode of transmission
Humans are the only source of these bacteria; no animal or environmental reservoirs have been identified. Typhoid and paratyphoid fever are most often acquired through consumption of water or food that has been contaminated by feces of an acutely infected or convalescent person or a chronic, asymptomatic carrier. Transmission through sexual contact, especially among men who have sex with men, has rarely been documented.