CDC, several states, and the U.S. Department of Agriculture Animal and Plant Health Inspection Service are investigating a multistate outbreak of Salmonella Enteritidis infections. CDC began investigating in December 2017 when CDC PulseNet identified a cluster of three Salmonella Enteritidis infections that whole genome sequencing showed were closely related genetically. A review of the PulseNet database identified six more closely related illnesses dating back to 2015. These illnesses were added to the outbreak case count. Nine people infected with the outbreak strain of Salmonella Enteritidis have been reported from eight states.