Connecticut Epidemiologist Newsletter   •   March 2023   •   Volume 43, No 2

Multi System Inflammatory Syndrome in Children (MIS-C) — Connecticut, April 2020 - December 2022

Multisystem inflammatory syndrome in children (MIS-C) is a delayed hyperinflammatory condition first recognized in April 2020 that can follow an infection with the SARS-CoV-2 virus (1). In May 2020, the Centers for Disease Control and Prevention (CDC) disseminated a health advisory requesting clinicians report suspected cases to local and state health departments using a clinical case definition. MIS-C was officially added to the List of Reportable Diseases, Emergency Illnesses and Health Conditions in Connecticut on January 1, 2021 (2). Beginning in January 2023, a new case definition for MIS-C standardized surveillance was adopted and is now referred to as the CSTE/CDC MIS-C surveillance case definition. Given the limited knowledge of MIS-C early on, the original clinical case definition was broad. The 2023 CSTE/CDC case definition has greater specificity allowing for the differentiation between MIS-C and other hyperinflammatory conditions, including Kawasaki disease and toxic shock syndrome. This article summarizes the MIS-C cases reported among Connecticut residents under 21 years of age between April 2020–December 2022 under the original clinical case definition and highlights updates to the CSTE/CDC MIS-C case definition for MIS-C moving forward.

Between April 2020–December 2022, 137 cases of MIS-C that met the clinical case definition were reported to the Connecticut Department of Public Health (CT DPH) (Table 1). Of these, 78 (57%) were male. The median age was eight years (range 10 months–19 years), with the highest incidence in children under the age of ten years old. MIS-C disproportionately impacted non-Hispanic Black populations, with an incidence rate of 36.77 cases per 100,000, and Hispanic/Latinx populations (17.69). This is consistent with national data (CDC, 2022). Cases were reported in all eight Connecticut counties with New Haven County having the highest incidence rate at 24.91 per 100,000, followed closely by 
Fairfield County at 21.18. Eighty-five percent of cases were not vaccinated against COVID-19 (Table 2).  All cases had at least one positive SARS-CoV-2 test, with the majority having a positive SARS-CoV-2 IgG antibody test (n=85, 63%). There were no fatalities, but 30.66% of cases were admitted to the intensive care unit.


The 2023 CSTE/CDC MIS-C surveillance case definition was developed after a review of 2020–2022 data in consultation with MIS-C experts (3). This definition was created to reduce the risk of misclassification during public health surveillance. Changes to the clinical criteria include a focus on C-reactive protein as the laboratory marker of systemic inflammation and multiple changes to the organ systems, clinical signs and symptoms that are used to define a MIS-C case. Laboratory criteria changes include the extension from 30 to 60 days for having a positive SARS-CoV-2 test (viral or antibody) or close contact with a confirmed or probable case prior to hospitalization.

Limitations of this analysis based on the original clinical case definition include the potential for underreporting and the inclusion of hyperinflammatory conditions caused by multiple etiologies. However, with the updated 2023 surveillance case definition for MIS-C, there is an increased ability to differentiate MIS-C from other hyperinflammatory conditions.

Healthcare providers should remain alert to the possibility of MIS-C among their patients due to the potential severity. Additionally, providers should test for IgG antibodies in suspect MIS-C cases; less than 6% of cases had a positive viral test at the time of MIS-C diagnosis. Suspected cases of MIS-C should continue to be reported to the Connecticut DPH Epidemiology and Emerging Infections Program.  Healthcare providers should complete the new CDC MIS-C case report form ( for each case identified and fax it to the CT DPH at (860)-629-6962 . For guidance on completing the updated case report form with the new definition, please view ( The updated CSTE/CDC MIS-C Surveillance Case Definition and the supporting evidence can be found here.

Reported by                                                                                                                                                                  A Gartman, MPH 
Acknowledgements                                                                                                                                                 R Angulo, MD, MBA; C Powell , MS.


  1. Riphagen, S., Gomez, X., Gonzalez-Martinez, C., Wilkinson, N., & Theocharis, P. (2020). Hyperinflammatory shock in children during COVID-19 pandemic. The Lancet, 395(10237), 1607–1608.
  2. Mullins, J., Carter, M. L., & Ertel, S.-H. (Eds.). (2021, January). The Connecticut Epidemiologist. The Connecticut Epidemiologist Newsletter. Retrieved September 29, 2022, from
  3. Melgar M, Lee EH, Miller AD, et al. Council of State and Territorial Epidemiologists/CDC Surveillance Case Definition for Multisystem Inflammatory Syndrome in Children Associated with SARS-CoV-2 Infection — United States. MMWR Recomm Rep 2022;71(No. RR-4):1–14. DOI:


       This page last updated 03/28/2023.