COVID-19 outbreak toolbox

COVID-19 outbreak toolbox

Updated | July 2024

Welcome to the COVID-19 toolbox

Key reference documents

Case definitions

Suspected case of SARS-CoV-2 infection 

(3 options)

A. A person who meets the clinical OR epidemiological criteria:

Clinical criteria:

  1. Acute onset of fever AND cough (ILI); OR
  2. Acute onset of ANY THREE OR MORE of the following signs or symptoms: fever, cough, general weakness/fatigue1, headache, myalgia, sore throat, coryza, dyspnoea, anorexia/nausea/diarrhoea

OR

Epidemiological criteria2:

  • contact of a probable or confirmed case, or linked to a COVID-19 cluster3
    1. Residing or working in a setting with high risk of transmission of the virus: for example, closed residential settings and humanitarian settings, such as camp and camp-like settings for displaced persons, any time within the 14 days before symptom onset; OR
    2. Residing in or travel to an area with community transmission anytime within the 14 days before symptom onset; OR
    3. Working in a health setting, including within health facilities and within households, anytime within the 14 days before symptom onset.

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

C. person with no clinical signs and symptoms or meeting epidemiologic criteria with a positive professional-use or self-test SARS-CoV-2 Antigen-RDT.4

Probable case of SARS-CoV-2 infection 

(2 options)

A. A patient who meets clinical criteria AND is a contact of a probable or confirmed case, or linked to a COVID-19 cluster3

B. Death, not otherwise explained, in an adult with respiratory distress preceding death AND who was a contact of a probable or confirmed case or linked to a COVID-19 cluster 3

Confirmed case of SARS-CoV-2 infection 

(2 options)

A. A person with a positive Nucleic Acid Amplification Test (NAAT), regardless of clinical criteria OR epidemiological criteria

B. 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.4

Note: 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.

WHO COVID-19: case definitions: updated in Public health surveillance for COVID-19, 22 July 2022 (Geneva: World Health Organization; 2022).

Definition of a contact of a case

A person who has had any one of the following exposures to a probable or a confirmed case of SARS-CoV-2 infection:

  • face-to-face contact with a probable or confirmed case within 1 metre and for at least 15 minutes, or
  • direct physical contact with a probable or confirmed case, or
  • direct care for a patient with probable or confirmed COVID-19 disease without the use of recommended personal protective equipment (PPE)23 or,
  • other situations as determined by local health authorities based on local risk assessments.

Exposure must have occurred during the infectious period of the case, which is defined as follows.

- Exposure to a symptomatic case: 2 days before and 10 days after symptom onset of the case,  plus 3 days without symptoms or 3 days with improving symptoms, for a minimum period of 13 days after symptoms onset.

- Exposure to an asymptomatic case: 2 days before and 10 days after the date on which the sample that led to confirmation was taken. 

1. Signs separated with slash (/) are to be counted as one sign.

2. In light of the heightened transmissibility of emerging variants and the high likelihood that any close contact could be infected, epidemiological criteria alone are included in order to qualify asymptomatic contacts for testing, when possible, for the countries with the capacity to adapt more sensitive testing strategies; this is particularly relevant in high-risk populations and settings

3. 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 linked, symptomatic (meeting clinical criteria of Suspect case definition A or B) persons with positive professional use OR self-test
Ag-RDT (based on ≥97% specificity of test and desired >99.9% probability of at least one positive result being a true positive)

4. Ag RDT 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 sample collection, test performance and
    result interpretation are done by a trained operator
  • Self-test SARS-CoV-2 antigen-RDT: WHO EUL-approved Ag-RDT in which sample collection, test performance and result interpretation
    are done by individuals by themselves.

     

    Data collection tools