A COVID-19 exposure occurs when an individual has close contact with someone who has a confirmed COVID-19 infection or a medical diagnosis of the illness. This typically means being within six feet of an infected person for a cumulative total of 15 minutes or more over a 24-hour period, regardless of mask usage. Testing after exposure helps determine infection status and limit community transmission.
COVID-19 Incubation Period
The incubation period for COVID-19 is the time between exposure and symptom onset or when the virus becomes detectable by a test. This period can vary, but it averages around 5 days. Symptoms may appear anywhere from 2 to 14 days after exposure. Testing too early can result in a false negative, as the viral load may not yet be high enough for detection.
When and How to Test
If you do not have symptoms, it is recommended to wait at least 5 full days after the last exposure before testing. Testing earlier increases the likelihood of inaccurate results. If symptoms develop, test immediately, regardless of the exposure timeline.
Two main types of tests are available: rapid antigen tests and PCR tests. Rapid antigen tests detect viral proteins and provide quick results, often within minutes. They are most accurate with a higher viral load, typically when a person is more contagious. However, they are less sensitive than PCR tests and may not detect the virus effectively early in an infection or in asymptomatic individuals.
PCR (polymerase chain reaction) tests, also known as molecular tests, look for the virus’s genetic material. They are more accurate and sensitive than rapid antigen tests, detecting smaller amounts of the virus. PCR tests are processed in a laboratory and take longer to yield results, but offer a more reliable negative result, especially if taking only one test. If an antigen test is negative after exposure, repeat the test after 48 hours, and potentially a third time 48 hours after the second negative result, to increase accuracy.
Understanding Your Test Results and Next Steps
A positive COVID-19 test result indicates the virus was detected. If you test positive, it is important to follow public health guidelines, which typically include isolating yourself from others to prevent further spread. Monitoring your symptoms and seeking medical advice, especially if you have risk factors for severe illness, is also important. Informing close contacts allows them to take necessary precautions.
A negative test result means the test did not detect the virus, but it does not completely rule out an infection. False negative results can occur if testing is done too early in the infection when the viral load is low, or if the test is not performed correctly. Even with a negative result, continued monitoring for symptoms is important, and precautions such as wearing a mask and practicing good hygiene should be maintained. If symptoms develop after a negative test, retesting is recommended. Public health authorities, such as the CDC, provide comprehensive guidance on isolation, precautions, and when to seek medical care, and these resources should be consulted for specific recommendations.