Council of State and Territorial Epidemiologists/CDC Surveillance Case Definition for Multisystem Inflammatory Syndrome in Children Associated with SARS-CoV-2 Infection - United States.

Since May 14, 2020, CDC has conducted national surveillance for multisystem inflammatory syndrome in children (MIS-C) associated with infection with SARS-CoV-2, the virus that causes COVID-19, among persons aged <21 years using a CDC case definition based on public health need and data from early reports of patients with this condition. Recent analyses of accumulated data indicated that certain criteria from the 2020 CDC MIS-C case definition performed better than others in distinguishing MIS-C from other illnesses and that certain other criteria likely contributed to misclassification. To incorporate lessons learned from MIS-C surveillance and public health investigations and to improve feasibility of implementation by surveillance staff at state, local, territorial, and tribal health departments, the Council of State and Territorial Epidemiologists (CSTE) and CDC developed a CSTE/CDC position statement (approved by CSTE in 2022) that includes an MIS-C surveillance case definition for voluntary reporting to CDC (effective January 1, 2023): This report summarizes the evidence and rationale supporting the components of the CSTE/CDC MIS-C surveillance case definition and describes the methods used to develop the definition. These methods included convening MIS-C clinical experts (i.e., consultants): regarding identification of MIS-C and its distinction from other pediatric conditions, a review of available literature comparing MIS-C phenotype with that of pediatric COVID-19 and other hyperinflammatory syndromes, and retrospective application of different criteria to data from MIS-C cases previously reported to CDC. The CSTE/CDC surveillance case definition for MIS-C includes four important changes, in comparison with the 2020 CDC MIS-C case definition. These changes are 1) no required duration of subjective or measured fever; 2) requirement of C-reactive protein ≥3.0 mg/dL to indicate systemic inflammation; 3) adjustments to criteria of organ system involvement to include addition of shock as a separate category and elimination of respiratory, neurologic, and renal criteria; and 4) new requirements on timing of positive SARS-CoV-2 laboratory testing relative to the MIS-C illness. Although MIS-C is not a nationally notifiable condition and reporting is voluntary, CSTE and CDC recommend that all states and territories report all cases meeting confirmed, probable, or suspect criteria of the CSTE/CDC MIS-C surveillance case definition beginning January 1, 2023, for cases with MIS-C illness onset on or after that date: