infectious disease similar to typhoid (typhoid fever), though usually milder, caused by any of several organisms: Salmonella paratyphi (paratyphoid A), S. schottmulleri (paratyphoid B), or S. hirschfeldii (paratyphoid C). The means of infection, spread, clinical course, pathology, diagnosis, prevention, and treatment are similar to those for typhoid.

Whereas typhoid and paratyphoid A are strictly human diseases, the paratyphoid B organism has been found in other animals and fowl, and accordingly these represent additional means of contamination of food and water. See also typhoid (typhoid fever).