When a person has close contact with an individual confirmed to have COVID-19, they have experienced an exposure. Close contact generally involves being within six feet of the infected person for a cumulative total of fifteen minutes or more over a 24-hour period. This exposure triggers a period of caution because the virus can take several days to cause a detectable infection. The primary goal following exposure is to prevent onward transmission through monitoring and risk reduction.
Clarifying Terminology: Quarantine Versus Isolation
The terms “quarantine” and “isolation” are often used interchangeably, yet they describe two different public health actions based on a person’s current health status. Quarantine refers to separating an individual who has been exposed to a contagious disease but is not yet displaying symptoms. This measure is a precaution taken when a person may be incubating the virus.
Isolation, by contrast, is the action taken when a person is currently sick or has tested positive for the virus, regardless of symptoms. Isolation keeps confirmed cases away from others to prevent immediate transmission. This guidance focuses on the post-exposure period, which primarily involves monitoring that has largely replaced the traditional, strict quarantine requirement for most people.
Determining the Duration Based on Status
Current recommendations shift the focus from mandatory staying home to strict monitoring and masking following exposure. This change reflects high levels of population immunity gained through vaccination and prior infection. The monitoring period for everyone, regardless of their vaccination or prior infection history, lasts for ten full days following the last known exposure.
The day of the last contact with the infected person is designated as Day 0, and the first full day after that contact is considered Day 1. This marks the start of the ten-day monitoring period. During this time, the exposed person should consistently check for any signs or symptoms of illness. If symptoms develop at any point, the individual must immediately transition to the full isolation guidance.
Scenario A: Up-to-date Status
For individuals who are up-to-date on their vaccinations or have had a documented infection within the past 90 days, traditional quarantine is not recommended. These individuals benefit from existing immune protection against severe illness. Instead of staying home, they must strictly adhere to wearing a high-quality mask for the entire ten-day post-exposure period.
This ten-day span requires continuous vigilance for symptoms like fever, cough, or fatigue, which could signal a breakthrough infection. While these people can continue normal activities, they should avoid visiting high-risk settings where vulnerable individuals may be present. This approach balances a return to daily life with a precautionary measure to limit community spread.
Scenario B: Not Up-to-date Status
People not up-to-date on vaccinations or who have not recently recovered from a documented infection must also follow the ten-day masking and monitoring period. Although the traditional strict five-day quarantine is no longer standard, some local jurisdictions or workplaces may still mandate it. In the absence of such a mandate, the core action remains symptom monitoring and consistent use of a high-quality mask.
If local or institutional policy mandates a full quarantine, the requirement is typically to stay home for five full days, followed by five days of strict masking. The most stringent guidelines—whether local public health or workplace rules—should be followed. This precautionary period is designed to cover the maximum known incubation period of the virus.
Recommended Testing Schedule
Testing is a fundamental component of the post-exposure monitoring strategy, regardless of vaccination status or symptom presentation. The optimal time to test is at least five full days following the last exposure date. Testing earlier may yield a false negative result because the viral load may not yet be high enough to detect. If symptoms, even mild ones, develop at any point after exposure, an individual should test immediately without waiting for Day 5.
A positive result on any test requires an immediate shift to isolation protocols, which involves staying home and away from others. If the Day 5 test is negative, particularly if it is a rapid antigen test, repeat testing is highly recommended for confirmation. Antigen tests are less sensitive than PCR tests, meaning a negative result is less reliable than a positive one, especially in asymptomatic individuals.
For the highest certainty, a negative antigen test should be followed by a second antigen test taken 48 hours later. If both tests are negative, confidence increases that the virus is not currently active. If a person can only perform a single test, a Polymerase Chain Reaction (PCR) test is the most reliable option for a negative result, although results take longer to process.
Safety Measures During the 10-Day Monitoring Period
The ten-day period of monitoring is required because the virus can take a full ten days to manifest following exposure. Even if a Day 5 test is negative, the most important precaution is the continued use of a high-quality, well-fitting mask (such as an N95 or KN95) when around others through Day 10. This consistent masking prevents transmission if the infection is still developing or asymptomatic.
Individuals should avoid settings that pose a higher risk of transmission, such as crowded indoor spaces. Avoiding contact with people who are immunocompromised or otherwise at high risk for severe illness is also advised. Continued daily symptom monitoring is necessary for the entire ten-day period, as symptoms can still appear late in the incubation phase.
If symptoms appear after Day 10, the individual should test again immediately and begin isolation if the result is positive. The ten-day period is a window for managing risk. Maintaining these precautions ensures that a potential infection is not passed on to family members, coworkers, or the wider community.