Explore the recorded discovery and history of Shigella flexneri, with source links and stated limits.
S. flexneri is one of four Shigella species and, PHAC states, the leading cause of shigellosis in developing countries, while S. sonnei is the most common species in developed countries. Infection can follow ingestion of only 10 to 200 organisms, and CDC notes that swallowing just a small amount can make someone sick. Illness is usually a self-limited diarrheal or dysenteric episode. Because CDC’s public pages and the US estimates below describe Shigella as a genus, those numbers are labelled genus-level rather than specific to this species.
During a dysentery epidemic in 1897, Kiyoshi Shiga isolated and identified the causative organism, originally named Bacillus dysenteriae and later Shigella dysenteriae. That is a different species from the one in this profile; the genus Shigella is named after him.
LPSN records Shigella flexneri Castellani and Chalmers 1919, published in their Manual of Tropical Medicine, as a validly published and conserved name on the Approved Lists of 1980, with type strain ATCC 29903.
These references do not establish the first person ever infected. Discovery, naming and isolation milestones do not date biological origin or a patient zero.
Source check: 2026-09-19. Educational content; independent scientific review remains pending.