There are multiple types of COVID-19 tests.
The most common type analyzes samples from your respiratory tract for the presence of the COVID virus in your system. You might be asked to spit, or someone will swab the inside of your nose.
Real-time reverse transcription polymerase chain reaction (RT-PCR) tests detects the presence of viral genetic material, nucleic acid.
Antigen tests detect the presence of a specific viral protein or antigen. The antigen test for detecting the COVID-19 virus is relatively inexpensive and fast but generally is less sensitive than the RT-PCR test.
Test results may take hours to several days. The results show your infection level at the time the sample was collected. A negative result doesn’t mean you definitely are virus-free. A negative result can occur if you’re tested early after infection and there isn’t enough virus in your system to be detected. During that time, you can transmit the virus to others.
You can be infected with the COVID-19 virus even after receiving a negative test result for current infection, so it’s important to continue wearing a mask, keeping physical distance from others and frequently washing your hands.
An antibody test indicate whether you previously were infected with the COVID-19 virus. Antibodies are proteins that your body produces to help fight infections. The antibody test analyzes a blood sample for antibodies against COVID-19. It is unknown how long antibodies remain in your body after infection.
More research is needed to determine how long after infection antibodies can be detected. It is not known if a positive antibody test means that you will be protected from becoming reinfected by the COVID-19 virus or how long that protection will last.
Learn more about COVID-19 tests.
Johns Hopkins University has a COVID-19 testing tracker for monitoring changes in COVID-19 cases and testing capacity throughout the United States .