Outbreak of Multidrug-Resistant Shigella sonnei Infections in a Retirement Community

On October 22, 2018, the Vermont Department of Health (VDH) notified CDC’s Waterborne Disease Prevention Branch of an outbreak of diarrhea caused by Shigella sonnei among residents, visitors, and staff members of a retirement community in Chittenden County, the state’s most populous county. High-quality single nucleotide polymorphism (SNP) analysis predicted initial isolates were multidrug resistant (MDR), and were closely related to a concurrent multistate cluster (differing by 0–11 SNPs). In the United States, rates of MDR shigellosis are increasing; outbreaks of MDR shigellosis are more common among men who have sex with men and are rare in retirement community settings. CDC collaborated with VDH to identify additional cases, determine transmission routes, and recommend prevention and control measures.