The four species of Shigella are S. boydii, S. dysenteriae, S. flexneri and S. sonnei. Shigella sonnei causes over two-thirds of shigellosis in the United States, while Shigella flexneri accounts for the remaining one-third. Other species account for diseases in other countries. Shigella dysenteriae causes fatal epidemics in many nations.
Shigellosis typically results in fever, vomiting and diarrhea, and it may result in severe dehydration that requires hospitalization. Laboratory tests identify the shigellosis bacteria. Some bacteriology laboratories may not perform the tests unless instructed to do so. Laboratories may also perform tests to identify the type of Shigella, as well as the appropriate antibiotics to treat it, if needed.