CDC is collaborating with the U.S. Department of Agriculture's Animal and Plant Health Inspection Service (USDA-APHIS) and state health departments to investigate an outbreak of human Salmonella Typhimurium infections with an indistinguishable pulsed-field gel electrophoresis pattern linked to contact with pet hedgehogs. This outbreak strain is historically rare, with only one to two cases reported via PulseNet (the national molecular subtyping network for foodborne disease surveillance) annually since 2002. Since 2011, an increasing number of cases have been detected. PulseNet identified 14 human isolates in 2011, 18 in 2012, and two in 2013.