Date range (2020)	Definition of confirmed case	Definition of confirmed non‐case	Definition of suspect case	Definition of probable case	Role of serology in testing
10‐30 January	10‐30 January: no documentation to define at this time (before first date of global guidelines) 31 January onwards: a confirmed case is a person with laboratory confirmation of COVID‐19 infection, irrespective of clinical signs and symptoms. No prescribed test in laboratory guidelines, suggested tests from 10 January include broad coronavirus RT‐PCR (with sequencing of precise virus in test positives), whole genome sequencing, broad coronavirus serology on paired samples, microscopy, culture. (Lab 10 January) Four suggested tests from 17 January: broad coronavirus RT‐PCR (with sequencing of precise virus in test positives), NAAT for SARS‐CoV‐2 when it becomes available, whole genome sequencing, and broad coronavirus serology on paired samples States that once specific NAAT assays are developed and validated, confirmation will be based on specific detection of unique sequences of viral nucleic acid by RT‐PCR	None stated	No definition of 'suspect case' at this time, but case definitions for surveillance are defined as a combination of symptoms and exposure, with more severe symptoms requiring less evidence for exposure	No definition at this time	Serological testing may be useful to confirm immunologic response to a pathogen from a specific viral group, e.g. coronavirus. Best results from serologic testing requires the collection of paired serum samples (in the acute and convalescent phase) from cases under investigation.
31 January‐26 February		None stated	Suspect case defined as combination of symptoms and exposure, with more severe symptoms requiring less evidence for exposure	A suspect case with inconclusive laboratory results or is test‐positive using a pan‐coronavirus assay without laboratory evidence of other respiratory pathogens (global 31 January)
27 February‐1 March		None stated	Suspect case defined as combination of symptoms and exposure, with more severe symptoms requiring less evidence for exposure, OR defined by symptoms requiring hospitalisation and an absence of alternative explanation	A suspected case with inconclusive laboratory results (global 27 February)
2 March‐19 March	A person with laboratory confirmation of COVID‐19 infection, irrespective of clinical signs and symptoms (global 31 January, 27 February, 20 March) Laboratory confirmation of cases by NAAT specific to SAR‐CoV‐2 such as real‐time reverse‐transcription polymerase chain reaction (rRT‐PCR) with confirmation by nucleic acid sequencing when necessary. The viral genes targeted so far include the N, E, S and RdRP genes. In areas with no known COVID‐19 virus circulation confirmation requires: NAAT‐positive for at least two different targets on the COVID‐19 virus genome, of which at least one target is preferably specific for COVID‐19 virus (or SARS‐like coronavirus) using a validated assay; OR NAAT‐positive result for betacoronavirus, and COVID‐19 virus identified by sequencing partial/whole genome of virus (sequence target larger or different from the amplicon probed in the NAAT assay) Discordant results should be resampled. In areas where COVID‐19 virus is widely spread, a simpler algorithm might be adopted (e.g. RT‐PCR of a single discriminatory target)	One or more negative results do not rule out the possibility of COVID‐19 virus infection.			In cases where NAAT assays are negative and there is a strong epidemiological link to COVID‐19 infection, paired serum samples (in the acute and convalescent phase) could support diagnosis once validated serology tests are available. Serological assays will play an important role in research and surveillance but are not currently recommended for case detection.
19 March‐present				Probable case A suspect case for whom testing for the COVID‐19 virus is inconclusive OR A suspect case for whom testing could not be performed for any reason
NAAT: nucleic acids amplification test; RT‐PCR: reverse transcription polymerase chain reaction; Source: WHO 2020 .