COVID-19 testing involves analyzing samples to assess the current or past presence of SARS-CoV-2. The two main branches detect either the presence of the virus or of antibodies produced in response to infection.Molecular tests for viral presence through its molecular components are used to diagnose individual cases and to allow public health authorities to trace and contain outbreaks. Antibody tests (serology immunoassays) instead show whether someone once had the disease.They are less useful for diagnosing current infections because antibodies may not develop for weeks after infection.It is used to assess disease prevalence, which aids the estimation of the infection fatality rate.

Individual jurisdictions have adopted varied testing protocols, including whom to test, how often to test, analysis protocols, sample collection and the uses of test results.This variation has likely significantly impacted reported statistics, including case and test numbers, case fatality rates and case demographics.Because SARS-CoV-2 transmission occurs days after exposure (and before onset of symptoms) there is an urgent need for frequent surveillance and rapid availability of results.