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How long does it take to find out if you’ve been exposed to coronavirus?

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Say you take a coronavirus test on a Friday. By Saturday, would the test you’ve taken be able to identify an active infection?

This is just one of the plethora of logistical questions that comes with dealing with COVID-19. The incubation period of this virus is still variable, depending on your individual biology, according to a recent study published in the Annals of Internal Medicine.

You see, the way that a virus afflicts you is dependent on an “incubation period”—the number of days between when you catch a pathogen and actually show symptoms. With COVID, things are even more complicated because you may not show symptoms at all.

But simply being asymptomatic doesn’t mean you can’t spread the pathogen to plenty of other people. The mathematics of virology reside on a logarithmic scale. (If you can potentially infect two people, then those two people can each infect two other people, you get to a whole lot of infections pretty quickly.)

And that’s precisely why it’s so important to know whether or not you may be actively carrying the coronavirus—a piece of information that may very well be dictated by exactly which kind of test you’re taking.

For instance, a rapid response “antigen test,” which may return results on-site within a half hour, will be a more useful piece of information than a test that takes three days to return.

There’s another complication: An active coronavirus infection conducted via a rapid antigen test—such as a 15 minute along the lines of Abbott’s—has a higher chance of returning a false negative result than one which may rely on polymerase chain reaction (PCR) technology, according to Harvard Medical School. So you may need to take both a rapid response test and a followup PCR test to confirm an active infection.

“If you test negative for COVID-19, you probably were not infected at the time your sample was collected,” says the Centers for Disease Control (CDC). “This does not mean you will not get sick: A negative test result only means that you did not have COVID-19 at the time of testing or that your sample was collected too early in your infection.”

The Annals of Internal Medicine study states that the median incubation period for coronavirus is about five days. But it can span the gamut from two days to two weeks, further complicating the convoluted web of coronavirus diagnostics.

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