The infection passes from the feces of an infected person during defecation to their hands and fingernails. Infection then passes to another person either directly by physical touch or indirectly by contaminated food. Outbreaks are common in homosexual men, under conditions of crowding and in circumstances where hygiene practices are poor, such as jails, daycare centres, mental hospitals and refugee camps. Illness may be severe in the elderly, those with underlying disease and persons with impaired immune systems. Shigellosis is caused by bacilli belonging to the Shigella family.
Occurrence is worldwide.
Outbreaks are common, particularly among homosexual men and in areas of overcrowding where sanitation is poor, such as jails, institutions for children, daycare centres, mental hospitals and crowded refugee camps. In general, S. flexneri , S. boydii , and S. dysenteriae 1 account for most cases in developing countries. In developed countries, S. sonnei is most common and S. dysenteriae is the least common. Multi-antibiotic resistant strains have appeared worldwide, resulting from wide spread use of antibiotics. The incubation period is usually quite brief, lasting for 12-96 hours.