July 21, 2021: Information in this article about disease progression, appropriate time interval between exposure and testing, and onset of infectiousness and symptoms is based on the SARS-CoV-2 viral variants in circulation at the time it was published. Since then, new variants of the virus have become prevalent, and some of this information has also changed. For example, individuals exposed to and infected with the now-dominant Delta variant tend to become sick faster, test positive earlier, and infect others sooner. Read more.
We’ve been getting a lot of questions from people who suspect they may have been exposed to the virus and are wondering what to do next. This newly updated, downloadable flowchart — and the information and links below — can help you assess your individual circumstances and choose the right course of action.
Was I exposed to the virus?
The answer to this question is likely to be “yes” if you had prolonged, close contact with someone who was both infected and infectious.
A person who has been exposed and infected is not immediately able to transmit the virus to other people. It generally takes at least two to three days after infection for the virus to replicate enough for that person to be able to infect others. In other words, if you spent time with an infected individual in the first two days after that person was exposed to the virus, your risk of having been exposed and infected is incredibly low. But after a few days have passed, the infected individual is increasingly likely to become contagious.
And at that point, they probably won’t have any symptoms. With COVID-19, people can begin transmitting the virus two to three days before their first symptoms appear. We also know that some infected people never develop symptoms at all but can still transmit the virus to others. So, if you spent time with someone during the two or three days before that person developed symptoms or tested positive, that is a potentially risky contact.
Someone who tested positive or developed symptoms of COVID-19 more than 10 days ago is no longer contagious, and should not be considered a risky contact, as long as they have been fever-free for 24 hours or more.
- I’ve been exposed to COVID-19; how soon will I be contagious?
- How long before symptom onset is a person contagious?
- Recovery from COVID-19: How long is someone contagious?
What kind of contact can transmit the virus?
Catching the virus from an infectious person requires “close contact.” The CDC defines that as being “within six feet of an infected individual for at least 15 cumulative minutes within a 24-hour period,” a definition that has proven to be a useful criterion for contact tracing.
The “six-feet rule” is based on the observation that large respiratory droplets are likely to fall to the ground within that distance. This guideline does not consider aerosols that do not settle to the ground immediately, but it still works fairly well, because aerosols are most concentrated near the person who released them. They become increasingly diluted (and, therefore, less harmful) over distance.
But you should also consider the environment. For example, in a closed, poorly ventilated room, it is possible that the virus could be transmitted over a longer distance or within a much shorter period of time. For the same reasons, in an outdoor environment with better airflow, it would likely require much closer contact and more time to transmit the virus from one person to another.
In any case, fleeting close encounters or brief conversations are very unlikely to lead to infection. Risk of viral transmission increases with increased time and decreased distance and ventilation.
What about testing?
You should be tested if you were exposed to the virus through contact with someone who has tested positive or who has developed symptoms after a known exposure AND if you were with that person at a time when they were likely to have been contagious.
Wait at least five days from the time of your possible exposure to be tested. The test is most likely to detect an infection 5–7 days after infection. A PCR test, rather than a rapid antigen test, will be the most accurate, especially if you still do not have symptoms. You should also follow your local public health authority's recommendations for self-quarantine, even if your COVID test comes back negative.