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Shigellosis is a diarrheal infection caused by Shigella bacteria, most commonly S. sonnei and S. flexneri. The organism is spread through the fecal-oral route and humans are the only known host. Food and water contaminated with human fecal matter are common vehicles of transmission. Because the infective dose of Shigella bacteria is very low, this infection is easily transmitted via household or sexual contact. Travelers to developing countries with poor sanitation are also at risk for infection.

Resources for the general public

  • Shigellosis facts, CDC

  • Sex and Shigellosis - Learn how to decrease sexual transmission of shigellosis and view a health advisory about cases in King County that have required hospitalization. Warning: Contains language and content targeted at individuals with sexual practices that increase the risk of shigellosis transmission.
    • Shigellosis (PDF, flyer): Increase in cases among men who have sex with men.

Resources for health care professionals


Purpose of surveillance:

  • To identify common source outbreaks
  • To identify and eliminate sources of transmission including contaminated food and water
  • To identify and eliminate person

Shigellosis case data

Local epidemiology:

Seventy-three confirmed and seven probable cases of shigellosis were reported in 2015, above the five-year average of 60 cases per year. Eighty percent of the cases were in males; thirteen (17%) of the cases were in children under age 18. Twenty (25%) of the cases required hospitalization; none died.
Shigella flexneri and S. sonnei accounted for 25 and 47 cases, respectively; one case of S. boydii was reported. Eighteen cases (23%) reported international travel during their exposure period, including travel to Asia and Pacific Islands (9), Mexico (5), Africa (2), South and Central America (1), and the Caribbean (1).
Thirty-eight (48%) of the cases reported in 2015 occurred among men who have sex with men; seventeen cases were known to be HIV-positive. Seattle and other cities in the United States have reported past outbreaks of shigellosis among men who have sex with men.

Each year in Washington state between 115 and 185 shigellosis cases are reported.