Exposure to COVID-19 is defined as being within six feet of an infected person for a cumulative total of 15 minutes or more over a 24-hour period, regardless of whether either person was wearing a mask. Understanding when to test after exposure is important for limiting further spread.
Understanding the Incubation Period
The incubation period for COVID-19 is the time between infection and symptom onset. This period commonly ranges from 2 to 14 days, with an average of about 5 days. During this time, the virus replicates within the body.
Testing too early can lead to an inaccurate negative result, known as a false negative. This occurs because the viral load may not yet be high enough for the test to detect it. Waiting for the viral load to increase ensures a more reliable test outcome.
When to Test After Exposure
For individuals exposed to COVID-19 who are not experiencing symptoms, the recommendation is to wait at least five full days after the last exposure before getting tested. This timeframe allows sufficient time for the viral load to become detectable. “Day 0” is considered the day of the last known exposure, with “Day 1” being the first full day following that exposure.
If symptoms develop at any point before the recommended five-day waiting period, testing should occur immediately, regardless of the exposure timeline. Symptoms like fever, cough, or fatigue indicate the virus may be active, warranting immediate testing. After exposure, monitor for symptoms for a full 10 days, even if an initial test is negative.
Test Types and Post-Exposure Guidance
Two common types of COVID-19 tests are rapid antigen tests and PCR tests. Rapid antigen tests are convenient for their quick results, but they generally have lower sensitivity compared to PCR tests, especially early in an infection or when viral loads are low. PCR tests are more sensitive and can detect the virus earlier and for a longer duration. If a rapid antigen test is negative but symptoms are present, repeating the rapid test after 48 hours or obtaining a more sensitive PCR test is advisable.
After exposure, taking precautions helps reduce potential spread. These steps include wearing a high-quality mask when around others and monitoring for symptoms for 10 days. If a test result is positive, isolation is recommended. Stay home until symptoms improve and you have been fever-free for at least 24 hours without medication. Even after isolation, take additional precautions, such as masking, for five more days.