Enteric fever, also known as typhoid fever, is caused by the bacteria Salmonella Typhi (S Typhi) and Salmonella Paratyphi A and B. The pathogenesis of enteric fever depends on a number of factors including the infecting species and infectious dose. Ingested organisms survive exposure to gastric acid before gaining access to the small bowel, where they penetrate the epithelium, enter the lymphoid tissue, and disseminate via the lymphatic or hematogenous route.