Health Care Providers
Communicable Diseases, Epidemiology and Immunization
March 27, 2007
Health Advisory: Shigellosis in King County
Action Requested
- Be alert for patients with symptoms of possible Shigella infection
- Obtain stool cultures for patients with compatible symptoms
- Obtain antibiotic susceptibility testing on Shigella isolates
- Exclude cases and ill contacts from settings with a high risk of transmission to others (child care attendees and workers, health care workers, food workers)
- Clinicians should report suspected or confirmed cases of shigellosis to Public Health at 206-296-4774
Background
From January 8, 2007 to March 12, 2007, Public Health Seattle King County received reports of 6 confirmed and 12 suspected cases of Shigella sonnei infection affecting primarily children age 2 to 8 years old and their contacts. Pulse Field Gel Electrophoresis (PFGE) testing has revealed that isolates from 5 out of 6 of the confirmed cases have genetic fingerprints that are indistinguishable, with the 6th isolate closely related. Our investigation has not uncovered either a common source or an epidemiologic link between the cases, however many of the cases share either residence in or frequent travel to Renton. Increased case finding may help establish the source of the infections.
Shigella is spread through the fecal-oral route, has a low infective dose and spreads readily from person to person in households and in group settings with young children. Illness usually begins 1 to 4 days after exposure and may last 4 to 7 days. The spectrum of illness ranges from asymptomatic to severe invasive disease with colitis. Symptoms include diarrhea (which may be watery or bloody), fever, abdominal cramps, and nausea or vomiting. Severe cases may be complicated by dehydration or seizures, especially in young children.
The diagnosis of shigellosis is important to establish and is made by culture of the stool. Antibiotic therapy decreases the severity and duration of illness. In King County and nationally, most isolates are resistant to ampicillin and trimethoprim-sulfamethoxazole, making it important that antibiotic susceptibility testing is done for all Shigella isolates. Untreated cases may asymptomatically shed the bacteria in their stool for days to months. Therefore antibiotic treatment is recommended for those with severe disease, immune deficiency, or at high risk of transmission to others (child care attendees and workers, health care workers, food workers, and men who have sex with men). Antidiarrheal agents are not recommended.
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