How common are Shigella infections and Shigella outbreaks?
The number of shigellosis cases reported annually to the Centers for Disease Control and Prevention (CDC) has varied over the past several years. National surveillance for Shigella infections is done through testing at state and territorial laboratories, the data from which is then collected in the Laboratory-based Enteric Disease Surveillance (LEDS) system. According to recent LEDS reports, Shigella infections decreased from over 14,000 isolates reported in 2008 to all-time lows of 7,000-8,000 isolates reported annually in 2011-2013. In 2016, the number of reported isolates was approximately 12,500. However, a majority of shigellosis cases go undiagnosed or unreported.
In a systematic review of global shigellosis cases from 1990 to 2016, researchers demonstrated that, while the burden of diarrhea attributable to Shigella and enterohemorrhagic E. coli was decreasing, these foodborne illnesses remained a substantial cause of mortality and disability globally. These findings pointed to the need for continued efforts to improve treatment, increase prevention, and reassess the effects on people older than five years.