The Prevalence of Shigella in Food and Elsewhere
Large Shigella outbreaks have been traced to contaminated food and water.
The CDC estimates that 450,000 to 500,000 total cases of shigellosis occur in the U.S. every year. The CDC does not classify shigellosis by a seasonal pattern; according to the agency, its incidence is driven by outbreaks. But, there is conflicting evidence suggesting the seasonality of Shigella infection, where incidence is connected with weather higher in temperature and precipitation. A confounding factor related to potential shigellosis seasonality is the fact that warmer months are typically when events including traveling, recreational water, and person-to-person contact increase, all of which are factors that contribute to outbreaks of Shigella.
Shigella is an especially common cause of disease among young children, in large part because it is difficult to control the spread of the bacteria in daycare settings. The symptoms of shigellosis vary so widely that children shedding Shigella in their stool may exhibit no symptoms of infection. A person infected with Shigella can be asymptomatic (i.e. show no symptoms of illness), suffer from moderate to severe diarrhea, or suffer complications up to and including death.