< Tests
What are the tests to find out if I have already had the COVID-19 ?
Text updated on 2021-05-09
Following a viral infection, the body protects itself with an immune response, involving the production of antibodies. Even when the virus has been defeated and eliminated, the antibodies persist in the blood and can be detected by a so-called serological test.
The serological test is used to find out if you have ever been infected with the SARS-CoV-2 coronavirus. A serologic test is a blood test to determine if a person has been previously exposed to a particular pathogen by examining their current immune response. Serological tests can provide information about the spread of disease in a population by identifying individuals who have developed antibodies to the virus. The results of these tests are available between 10 minutes and 5 days. Several highly reliable tests have been developed.
Serological tests measure the presence of antibodies in blood serum and, thus, analyze the antibody composition in the blood. They are increasingly in demand to quantify the number of people who have been infected, including those with mild or no symptoms, or those who have already recovered. A positive serological test does not mean that a person is contagious.
Serological tests differ from RT-qPCR tests, currently used worldwide to diagnose COVID-19 cases, which only indicate the presence of viral material during infection but not whether a person has been infected and subsequently recovered.
Antibodies against the virus appear after a few days. Having antibodies against the virus SARS-CoV-2 seems to prevent future infection but it is not yet known how long this immune protection lasts. See the question Can you catch COVID twice? There is too little experience to know how long the immune protection lasts. We must therefore remain cautious.
In conclusion
YES, the serological test is a reliable test.
NO, a positive test doesn't mean you're contagious.
A positive test suggests immunity, but there is no certainty about the degree and duration of protection.
Sources
John Hopkins University Synthesis on Serological Testing
developed mainly by the United States, China, South Korea, Singapore, Germany, and England.Detection of SARS-CoV-2 viruses in people who have already been infected and developed COVID-19 in Korea: Observations on patients in South Korea show that some patients already infected and with antibodies against the virus may re-develop the disease COVID-19 and present viral material in their nasopharyngeal secretions again. It is not yet clear at this stage whether the patients have been re-infected or have never really cleared the virus.
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