Coronavirus Disease 2019 (COVID-19)
2023 Case Definition

Background

In late December 2019, investigation of a cluster of pneumonia cases of unknown origin in Wuhan, China resulted in identification of a novel coronavirus. The virus is distinct from although closely related to both severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV).¹

Those at highest risk for severe disease and death include people aged over 60 years (especially those 85 years and older) and those with underlying conditions, including but not limited to obesity, hypertension, diabetes, cardiovascular disease, chronic respiratory or kidney disease, immunosuppression from solid organ transplant, and sickle cell disease. A complete list can be found at: https://www.cdc.gov/coronavirus/2019-ncov/need-extra-precautions/people-with-medical-conditions.html.

Because of the continual advancement in the science of COVID-19 disease and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and changes to surveillance approaches during the pandemic, CSTE approved revised position statement 22-ID-01 in June 2022 to update reporting and case classification criteria to better meet long-term surveillance goals for tracking this disease. Universal case investigation and contact tracing is no longer an effective intervention for containing spread. Further, surveillance for probable cases based on clinical criteria and epidemiologic linkage to known cases is no longer necessary. COVID-19 case ascertainment based on positive serologic test results is also no longer relevant, as surveillance should focus on incident cases only.

Laboratory Criteria

Laboratory evidence using a method approved or authorized by the U.S. Food and Drug Administration (FDA)² or designated authority^*:

Confirmatory** laboratory evidence:

• Detection of SARS-CoV-2 ribonucleic acid (RNA) in a clinical or post-mortem specimen using a diagnostic molecular amplification test performed by a Clinical Laboratory Improvement Amendments (CLIA)-certified provider***, OR
• Detection of SARS-CoV-2 RNA in a clinical or post-mortem specimen by genomic sequencing****.

Presumptive** laboratory evidence:

• Detection of SARS-CoV-2 specific antigen in a clinical or post-mortem specimen using a diagnostic test performed by a CLIA-certified provider.***

Supportive** laboratory evidence:

• Detection of SARS-CoV-2 specific antigen by immunocytochemistry, OR
• Detection of SARS-CoV-2 RNA or specific antigen using a test performed without CLIA oversight.

*On March 13, 2020, the President issued a Memorandum on Expanding State-Approved Diagnostic Tests: “Should additional States request flexibility to authorize laboratories within the State to develop and perform tests used to detect COVID-19, the Secretary shall take appropriate action, consistent with law, to facilitate the request.” 

  **The terms confirmatory, presumptive, and supportive are categorical labels used here to standardize case classifications for public health surveillance. The terms should not be used to interpret the utility or validity of any laboratory test methodology.

*** Includes those tests performed under a CLIA certificate of waiver.     

****Some genomic sequencing tests that have been authorized for emergency use by the FDA do not require an initial polymerase chain reaction (PCR) result to be generated. Genomic sequencing results may be all the public health agency receives.

Criteria to Distinguish a New Case from an Existing Case

The following should be enumerated as a new case:

• Person was most recently enumerated as a confirmed or probable case with onset date (if available) or first positive specimen collection date for that classification >90 days prior^‡,

   OR

• SARS-CoV-2 sequencing results from the new positive specimen and a positive specimen from the most recent previous case demonstrate a different lineage,

  OR

• Person was previously reported but not enumerated as a confirmed or probable case (i.e., suspect)^‡‡, but now meets the criteria for a confirmed or probable case.

^‡Some individuals, e.g., severely immunocompromised persons, can shed SARS-CoV-2, as detected by molecular amplification tests, >90 days after  infection.  For severely immunocompromised individuals, clinical judgment should be used to determine if a repeat positive test is likely to result from long-term shedding and, therefore, not be enumerated as a new case. Severe immunocompromise conditions include chemotherapy for cancer, untreated human immunodeficiency virus (HIV) infection with CD4 T lymphocyte count <200, combined primary immunodeficiency disorder, and receipt of prednisone >20mg/day for more than 14 days.

 ^‡‡Repeat suspect cases should not be enumerated.

Suspect

• Meets supportive laboratory evidence,^† OR
• Meets vital records criteria with no confirmatory or presumptive laboratory evidence for SARS-CoV-2.

† For suspect cases, jurisdictions may opt to place them in a registry for other epidemiological analyses or investigate to determine probable or confirmed status. Suspect cases should not be included in case counts.

Probable

• Meets presumptive laboratory evidence.

Confirmed

• Meets confirmatory laboratory evidence.

Vital Records Criteria                                                                                                                                                                                             

A  death certificate that lists COVID-19 disease or SARS-CoV-2 or an equivalent term as an underlying cause of death or a significant condition contributing to death.

• Coronavirus Disease 2019 (COVID-19) | 2021 Case Definition
• Coronavirus Disease 2019 (COVID-19) | 2020 Interim Case Definition, Approved August 5, 2020
• Coronavirus Disease 2019 (COVID-19) | 2020 Interim Case Definition, Approved April 5, 2020