Spatial and space–time trends of reported Shigella spp. outbreaks in the United States, 2009-2022

Abstract

Shigella spp. are the leading cause of acute gastroenteritis, posing a public health concern in the United States. This study analyzed surveillance data on Shigella spp. outbreaks reported to the Centers for Disease Control and Prevention via the National Outbreak Reporting System from 2009 to 2022. A total of 1,208 outbreaks were reported across the 48 contiguous states and the District of Columbia; outbreak incidence varying significantly across time and space. State-level outbreak incidence rates were calculated and mapped across five multiyear periods. Moran’s I was used to identify local clusters and outliers. Poisson spatial and space–time scan statistics were applied to detect areas and periods of elevated or reduced outbreak rates. Persistent high-rate spatial and space–time clusters were identified in the Midwest, South, and Southwest, including Ohio, Texas, Minnesota, and Arizona. Prolonged low-rate clusters were concentrated in the Northeast and Mid-Atlantic regions. These findings demonstrate that Shigella spp. outbreaks in the United States exhibit persistent and regionally distinct spatiotemporal clustering patterns. Identifying areas with sustained elevated outbreak risk can support targeted surveillance, prevention, and response efforts.