Laboratory testing for the respiratory coronavirus disease 2019 (COVID-19) and the associated SARS-CoV-2 virus includes methods that detect the presence of virus and those that detect antibodies produced in response to infection.
The presence of viruses in samples is confirmed by RT-PCR, which detects the coronavirus' RNA. This test is specific and is designed to only detect the RNA of the SARS-CoV-2 virus. It is used to confirm very recent or active infections.
Detection of antibodies (serology) can be used both for diagnosis and population surveillance. Antibody tests show how many people have had the disease, including those whose symptoms were minor. An accurate mortality rate of the disease and the level of herd immunity can be determined from the results of this test.
Due to limited testing, as of March 2020 no countries had reliable data on the prevalence of the virus in their population. By 23 March, no country had tested more than 3% of their population, and there are massive variations in how much testing has been done across countries. This variability is also likely to be significantly affecting reported case-fatality rates.

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