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Public Health - Seattle & King County


Shigellosis is an enteric bacterial infection caused by Shigella species, 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.

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Shigellosis in King County

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-to-person spread of infection

Shigellosis Case Data in King County

Local epidemiology:

Sixty-seven cases of shigellosis were reported in 2012 representing an increase over previous years (5-year average: 48 cases); no outbreaks were identified. Seventy-one percent of the cases were in males; ten (15%) of the cases were in children under age 18 and under. One quarter of the cases required hospitalization, none died.

The majority of cases were caused by Shigella sonnei and S. flexneri, which accounted for 34 and 29 cases, respectively. Additional reports included S. boydii (3), and S. dysenteriae (1), untyped (1). Twelve cases reported international travel during their exposure periods, including travel to Asia and the Pacific (4), Africa (2), Mexico (3), South and Central America (2), and Canada (1). One case occurred in a recent immigrant from Asia.

Thirty (44%) of the cases reported in 2012 occurred among men who have sex with men, twenty of whom were known to be HIV-positive. Both the number and proportion of shigellosis cases that have been HIV+ have increased in recent years. Many of these cases denied sexual contact during their exposure period, or reported only one long-term partner without symptoms of illness. Seattle and other cities in the US have reported past outbreaks of shigellosis among men who have sex with men.

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