| Clinical
Features |
Watery or bloody diarrhea, abdominal
pain, fever, and malaise. |
| Etiologic
Agent |
Four species of Shigella: boydii,
dysenteriae, flexneri, and sonnei. |
| Incidence |
Approximately 14,000 laboratory
confirmed cases of shigellosis and an estimated 448,240 total
cases (85% due to S. sonnei) occur in the United States
each year. In the developing world, S.flexneri predominates.
Epidemics of S. dysenteriae type 1 have occurred in
Africa and Central America with case fatality rates of 5-15%. |
| Sequelae |
Reiter's syndrome is a late complication
of S. flexneri infection, especially in persons with
the genetic marker HLA-B27. Hemolytic-uremic syndrome can
occur after S. dysenteriae type 1 infection. Convulsions
may occur in children; the mechanism may be related to a rapid
rate of temperature elevation or metabolic alterations. |
| Transmission |
A small inoculum (10 to 200 organisms)
is sufficient to cause infection. As a result, spread can
easily occur by the fecal-oral route and occurs in areas where
hygiene is poor. Epidemics may be foodborne or waterborne.
Shigella can also be transmitted bu flies. |
| Risk
Groups |
In the United States, groups at
increased risk of shigellosis include children in child-care
centers and persons in custodial institutions, where personal
hygiene is difficult to maintain; Native Americans; orthodox
Jews; international travelers; men who have sex with men;
and those in homes with inadequate water for handwashing. |
| Surveillance |
All reported cases are laboratory-confirmed
in states or at CDC. Shigellosis is a notifiable infectious
disease. |
| Trends |
Decreasing incidence in cases since
1995; characteristically, S. sonnei causes large periodic
outbreaks. |
| Challenges |
Increasing resistance to available
antimicrobial agents among isolates acquired domestically
and abroad; absence of effective vaccines; modifying handwashing
behavior to control prolonged community-wide outbreaks; identifying
targeted prevention measures in high-risk groups (e.g., Native
Americans, Orthodox Jews, men who have sex with men, and children
who attend daycare). |
| Opportunities |
A major initiative to strengthen
laboratory, epidemiologic, and public health capacity to detect
and respond to epidemic S.dysenteriae type 1 in southern
Africa could be duplicated in other regions at risk. Partnerships
with local health departments and communities may lead to
investigations of transmission and new prevention materials.
Subtyping of S. sonnei by pulsed field gel electrophoresis
can improve outbreak detection and control. |
|
December 2003
|
