SARS-CoV-2 can be diagnosed using a PCR RNA test that detects viral genetic material in a nasal swab sample. Viral antigen tests, which can be done at home, detect fragments of viral proteins. These are less accurate than laboratory PCR tests. Testing positive on an antigen test indicates a current active infection.

The Centers for Disease Control and Prevention (CDC) advises that people who test positive and have no symptoms should stay home and avoid contact with others for five days, then continue to wear a mask and avoid vulnerable people through day 10. Those with mild symptoms can end isolation after five days if their symptoms are improving and they haven’t had a fever for 24 hours. People with moderate to severe illness should isolate for at least 10 days. Click here for CDC isolation recommendations.

Another type of COVID test detects SARS-CoV-2 antibodies in the blood, which show whether someone was infected in the past. However, not everyone who had COVID will have persistent antibodies.

Last Reviewed: September 15, 2023