COVID-19

=== Viral testing ===
{{Main|COVID-19 testing}}
[[File:Infektionsschutzzentrum im Rautenstrauch-Joest-Museum, Köln-6313 (cropped).jpg|thumb|Demonstration of a [[nasopharyngeal swab]] for [[COVID‑19 testing]]]]

The standard methods of testing for presence of SARS-CoV-2 are [[nucleic acid test]]s,<ref name="pmid32621814" /><ref name="20200130cdc">{{#invoke:Cite web||date=30 January 2020|title=2019 Novel Coronavirus (2019-nCoV) Situation Summary|url=https://www.cdc.gov/coronavirus/2019-ncov/summary.html|url-status=live|archive-url=https://web.archive.org/web/20200126210549/https://www.cdc.gov/coronavirus/2019-nCoV/summary.html|archive-date=26 January 2020|access-date=30 January 2020|website=U.S. [[Centers for Disease Control and Prevention]] (CDC)}}</ref> which detects the presence of viral RNA fragments.<ref name="WHO_InterimGuidance">{{#invoke:Cite web||title=Coronavirus disease (COVID-19) technical guidance: Laboratory testing for 2019-nCoV in humans |work=[[World Health Organization]] (WHO) |url=https://www.who.int/emergencies/diseases/novel-coronavirus-2019/technical-guidance/laboratory-guidance |access-date=14 March 2020 |archive-url=https://web.archive.org/web/20200315044138/https://www.who.int/emergencies/diseases/novel-coronavirus-2019/technical-guidance/laboratory-guidance |archive-date=15 March 2020 |url-status=live}}</ref> As these tests detect RNA but not infectious virus, its "ability to determine duration of infectivity of patients is limited".<ref name="2k0iS">{{#invoke:cite journal ||vauthors=Bullard J, Dust K, Funk D, Strong JE, Alexander D, Garnett L, Boodman C, Bello A, Hedley A, Schiffman Z, Doan K, Bastien N, Li Y, Van Caeseele PG, Poliquin G |title=Predicting Infectious Severe Acute Respiratory Syndrome Coronavirus 2 From Diagnostic Samples |journal=Clinical Infectious Diseases |volume=71 |issue=10 |pages=2663–2666 |date=December 2020 |pmid=32442256 |pmc=7314198 |doi=10.1093/cid/ciaa638 |doi-access=free |title-link=doi}}</ref> The test is typically done on respiratory samples obtained by a [[nasopharyngeal swab]]; however, a nasal swab or sputum sample may also be used.<ref name="CDC2020Testing">{{#invoke:Cite web||date=11 February 2020|title=Interim Guidelines for Collecting, Handling, and Testing Clinical Specimens from Persons for Coronavirus Disease 2019 (COVID-19) |url=https://www.cdc.gov/coronavirus/2019-ncov/lab/guidelines-clinical-specimens.html|url-status=live|archive-url=https://web.archive.org/web/20200304165907/https://www.cdc.gov/coronavirus/2019-nCoV/lab/guidelines-clinical-specimens.html|archive-date=4 March 2020|access-date=26 March 2020|website=U.S. [[Centers for Disease Control and Prevention]] (CDC)}}</ref><ref name="20200129cdc">{{#invoke:Cite web||date=29 January 2020|title=Real-Time RT-PCR Panel for Detection 2019-nCoV |url=https://www.cdc.gov/coronavirus/2019-ncov/lab/rt-pcr-detection-instructions.html|url-status=live|archive-url=https://web.archive.org/web/20200130202031/https://www.cdc.gov/coronavirus/2019-ncov/lab/rt-pcr-detection-instructions.html|archive-date=30 January 2020|access-date=1 February 2020|website=U.S. [[Centers for Disease Control and Prevention]] (CDC)}}</ref> Results are generally available within hours.<ref name="pmid32621814" /> The WHO has published several testing protocols for the disease.<ref>{{#invoke:Cite web||title=Laboratory testing for 2019 novel coronavirus (2019-nCoV) in suspected human cases|url=https://www.who.int/publications-detail/laboratory-testing-for-2019-novel-coronavirus-in-suspected-human-cases-20200117|url-status=live|archive-url=https://web.archive.org/web/20200317023052/https://www.who.int/publications-detail/laboratory-testing-for-2019-novel-coronavirus-in-suspected-human-cases-20200117|archive-date=17 March 2020|access-date=13 March 2020|website=[[World Health Organization]] (WHO)}}</ref>

Several laboratories and companies have developed serological tests, which detect antibodies produced by the body in response to infection. Several have been evaluated by [[Public Health England]] and approved for use in the UK.<ref name="independent9515466">{{#invoke:cite news||date=14 May 2020|title=NHS staff will be first to get new coronavirus antibody test, medical chief promises|website=The Independent|url=https://www.independent.co.uk/news/uk/home-news/coronavirus-test-antibody-covid-roche-immune-nhs-staff-a9515466.html|access-date=14 May 2020}}</ref>

The [[University of Oxford]]'s CEBM has pointed to mounting evidence<ref name="yFMEP">{{#invoke:Cite web|| vauthors = Heneghan C, Jefferson T |date=1 September 2020|title=Virological characterization of COVID-19 patients that test re-positive for SARS-CoV-2 by RT-PCR|url=https://www.cebm.net/study/virological-characterization-of-covid-19-patients-that-test-re-positive-for-sars-cov-2-by-rt-pcr|access-date=19 September 2020|website=CEBM}}</ref><ref name="2exX5">{{#invoke:cite journal || vauthors = Lu J, Peng J, Xiong Q, Liu Z, Lin H, Tan X, Kang M, Yuan R, Zeng L, Zhou P, Liang C, Yi L, du Plessis L, Song T, Ma W, Sun J, Pybus OG, Ke C  | title = Clinical, immunological and virological characterization of COVID-19 patients that test re-positive for SARS-CoV-2 by RT-PCR | journal = eBioMedicine | volume = 59 | pages = 102960 | date = September 2020 | pmid = 32853988 | pmc = 7444471 | doi = 10.1016/j.ebiom.2020.102960 }}</ref> that "a good proportion of 'new' mild cases and people re-testing positives after quarantine or discharge from hospital are not infectious, but are simply clearing harmless virus particles which their immune system has efficiently dealt with" and have called for "an international effort to standardize and periodically calibrate testing"<ref name="PQGAv">{{#invoke:Cite web|| vauthors = Spencer E, Jefferson T, Brassey J, Heneghan C |date=11 September 2020|title=When is Covid, Covid?|url=https://www.cebm.net/covid-19/when-is-covid-covid/|access-date=19 September 2020|website=The Centre for Evidence-Based Medicine}}</ref> In September 2020, the UK government issued "guidance for procedures to be implemented in laboratories to provide assurance of positive SARS-CoV-2 RNA results during periods of low prevalence, when there is a reduction in the predictive value of positive test results".<ref name="9Kblp">{{#invoke:Cite web||title=SARS-CoV-2 RNA testing: assurance of positive results during periods of low prevalence |url=https://www.gov.uk/government/publications/sars-cov-2-rna-testing-assurance-of-positive-results-during-periods-of-low-prevalence|access-date=19 September 2020|website=GOV.UK}}</ref>