Defining suspect, probable, and confirmed COVID-19 cases

Surveillance for COVID-19 remains critical to ending the COVID-19 emergency worldwide and informing public health actions to limit the spread of SARS-CoV-2 and reduce morbidity, mortality and impact. 

Please refer to the updated COVID-19 case definitions issued by the World Health Organization as of July 22, 2022:

Suspected case

1. A person who meets the clinical or epidemiological criteria:

Clinical Criteria:

• Acute onset of fever and cough; or
• Acute onset of any three or more of the following signs or symptoms: fever. Cough, general weakness/fatigue, headache, myalgia, sore throat, coryza, nausea/diarrhea/anorexia

Epidemiological Criteria:

• Contact of a probable or confirmed case, or linked to a COVID-19 cluster

2. A patient with severe acute respiratory illness (SARI: acute respiratory infection with history of fever or measure fever of ≥ 38°C; and cough; with onset within the last 10 days; and requires hospitalization).

3. A person without clinical signs or symptoms, NOR meeting epidemiologic criteria; or with a positive Professional Use or Self Test SARS-CoV-2 Antigen-RDT3

Probable case

• A patient who meets clinical criteria above AND is a contact of a probable or confirmed case, or linked to a COVID-19 cluster
• Death, not otherwise explained, in an adult with respiratory distress preceding death AND was a contact of a probable or confirmed case or linked to a COVID-19 cluster

Confirmed case

• A person with a positive Nucleic Acid Amplification Test (NAAT), regardless of clinical criteria OR epidemiological criteria; or
• A person Meeting clinical criteria AND/OR epidemiological criteria ( suspect case A) With a positive Professional Use or Self Test SARS-CoV-2 Antigen-RDT

Remember: Clinical and public health judgment should be used to determine the need for further investigation in patients who do not strictly meet the clinical or epidemiological criteria. Surveillance case definitions should not be used as the sole basis for guiding clinical management.

Notes:

1. Signs separated with a slash (/) are to be counted as one sign. 
2. COVID-19 cluster: A group of symptomatic individuals linked by time, geographic location, and common exposures, containing at least one NAAT-confirmed case or at least two epidemiologically related, symptomatic (meeting clinical criteria of Suspect case definition A or B) persons with positive health professional OR self-test Ag-RDTs (based on ≥97% specificity of test and desired >99.9% probability of at least one positive result being a true positive)
3. Ag RDT Test Antigen-detection Rapid Diagnostic Tests (Ag-RDT) are available for use by trained professionals or for self-testing by individuals: 

   - Professional Use SARS-CoV-2 Antigen-RDT: WHO EUL approved Ag-RDT, , in which a trained operator does sample collection, test performance, and result interpretation 

   - Self-test SARS-CoV-2 Antigen-RDT : WHO EUL approved Ag-RDT in which an individual does sample collection, test performance, and result interpretation by themselves

4. Typical chest imaging findings suggestive of COVID-19 include the following:

• • • Chest radiography: hazy opacities, often rounded in morphology, with peripheral and lower lung distribution 
    • Chest CT: multiple bilateral ground glass opacities, often rounded in morphology, with peripheral and lower lung distribution 
    • Lung ultrasound: thickened pleural lines, B lines (multifocal, discrete, or confluent), consolidative patterns with or without air bronchograms.

Source: World Health Organization. COVID-19 Case Definitions. Retrieved from: https://www.who.int/publications/i/item/WHO-2019-nCoV-Surveillance_Case_Definition-2022.1