In epidemic situations a clinical diagnosis is made by taking a history of symptoms from the patient and by a brief examination only. Treatment is usually started without or before confirmation by laboratory analysis of specimens.
Stool and swab samples collected in the acute stage of the disease, before antibiotics have been administered, are the most useful specimens for laboratory diagnosis. If an epidemic of cholera is suspected, the most common causative agent is Vibrio cholerae O1. If V. cholerae serogroup O1 is not isolated, the laboratory should test for V. cholerae O139. However, if neither of these organisms is isolated, it is necessary to send stool specimens to a reference laboratory. Infection with V. cholerae O139 should be reported and handled in the same manner as that caused by V. cholerae O1. The associated diarrheal illness should be referred to as cholera and must be reported as a case of cholera to the appropriate public health authorities.[15]
