Some persons who are infected may have no symptoms at all, but may still pass the Shigella bacteria to others. The Shigella germ is actually a family of bacteria that can cause diarrhea in humans. These microscopic living creatures, which can pass from person to person, were discovered 100 years ago by a Japanese scientist named Shiga, for whom they are named. There are several kinds of Shigella bacteria but only two are common in the United States. Many different kinds of diseases can cause diarrhea and bloody diarrhea.
Effective treatment depends on which germ is causing the diarrhea.
Determining that Shigella is the cause of the illness depends on laboratory tests that identify the bacteria in the stools of infected persons. These tests are sometimes not performed unless the laboratory is instructed specifically to look for the organism. The laboratory also can do special tests to tell which type of Shigella the person has and which antibiotics, if any, would be best to treat it. Because many milder cases are not diagnosed or reported, the actual number of infections may be 20 times greater. Shigellosis is particularly common and causes recurrent problems in settings where hygiene is poor and can sometimes sweep through entire communities.