In May and June of 2011, a team from the CDC assisted the South Sudan Ministry of Health and the WHO with an investigation of NS in Western Equatoria State in South Sudan. A total of 38 case-control pairs matched by age- and village- were identified for the case control investigation and separately, 25 subjects with reported NS were enrolled in a case series and underwent thorough medical and neurological evaluations (17). The findings from this investigation were consistent with the unpublished findings from investigations in Uganda in 2009-10, with the cause of Nodding syndrome continuing to remain unknown.