The Science Behind A 14-Day Quarantine After Possible COVID-19 Exposure

To stop the spread of the coronavirus, health officials have a favorite refrain: After being in a city or region where there have been a lot of COVID-19 cases, spend 14 days in quarantine even if you feel perfectly fine — don't leave your house. Coming from New York? 14-day quarantine. Arriving in Hawaii? 14-day quarantine. Been in Italy or China or Iran recently? 14-day quarantine.

"That's a long-standing public health practice, and it's called 'traveler's quarantine,' " explains Lindsay Wiley, a professor at American University's Washington College of Law. "Fourteen days is not a made-up number here — it's based on what we know so far about COVID-19, and it's possible that over time we'll see that number change as we learn more [about the virus]."

The 14-day rule is widespread because public health agencies around the world work together on these guidelines. In the U.S., the Centers for Disease Control and Prevention sets the quarantine period, and its counterpart organizations do so abroad, all in concert with the World Health Organization.

If you're one of the many people who are being asked to quarantine for a fortnight, you might be asking: Why 14 days, exactly?

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