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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.

Health Alert:

In 2016, there have been several cases of shigellosis reported in King County that have been serious enough to lead to hospitalization.  Most of these cases were among gay and bisexual men who contracted Shigella in bathhouse settings or through anonymous sexual contact.  While Shigella bacteria are often transmitted through improper hygiene and travel to areas with contaminated water and food, among gay and bisexual men, the primary transmission route is through oral-anal contact – including rimming and anal intercourse. The bacteria can be spread from hand to mouth, such as through the handling of used condoms, fingering or sharing of sex toys or equipment.  Left untreated, shigellosis is of particular danger to those living with HIV.

Gay and bisexual men who've experienced 48 hours or longer of diarrhea are encouraged to visit their primary health care provider and get tested for Shigella. Without proper treatment, shigellosis can be serious – especially to HIV+ individuals. Avoid hospitalization by seeking treatment early in the illness.

Shigellosis is sometimes asymptomatic and even in cases where the symptoms have cleared, infected persons can still transmit the bacteria to others for up to two weeks, either through poor hygiene or sexual contact. Protect your partners by avoiding sexual contact until advised by your physician and maintain good hygiene by washing your hands with soap and water after using the restroom.

More information on Shigella and Sex.

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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-two confirmed and three probable cases of shigellosis were reported in 2014, similar to the five-year average of 54 cases per year. Sixty-eight percent of the cases were in males; fourteen (22%) of the cases were in children under age 18. Sixteen (25%) of the cases required hospitalization; none died.

Shigella flexneri and S. sonnei accounted for 31 and 30 cases, respectively; one case of S. boydii was reported. Seventeen cases (26%) reported international travel during their exposure period, including travel to Asia and Pacific Islands (6), Mexico (4), Africa (3), South and Central America (1), Canada (1), Europe (1), and the Middle East (1).

Seventeen (26%) of the cases reported in 2014 occurred among men who have sex with men; eight 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.