A dysentery bacterium that needs only a tiny dose; the leading Shigella species in lower-income settings. Explore its illustrative 3D model, human context, and sources.
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.
The small dose needed for infection makes person-to-person and hygiene-related spread easy, which is why CDC names children under 5, travellers, gay and bisexual men and other men who have sex with men, and people experiencing homelessness among higher-risk groups. CDC also reports that antimicrobial-resistant Shigella infections result in an estimated 93 million dollars in direct medical costs. Species and serotype affect the clinical picture.
Original schematic 3D phenotype. PHAC describes Shigella as Gram-negative, rod-shaped, non-motile, non-encapsulated, non-sporulating facultative anaerobes. No flagella, capsule or endospore should be assigned, which distinguishes this silhouette from the flagellated enteric rods in the catalogue. Colours, dimensions, layer thicknesses and displayed arrangements are diagram choices, not a measured individual cell. Independent scientific review remains pending.
Source check: 2026-09-19. Educational content; independent scientific review remains pending.