What the U.S. CDC’s New Definition of ‘Close Contact’ Really Means

What the U.S. CDC’s New Definition of ‘Close Contact’ Really Means
Photo: Iakov Filimonov, Shutterstock

Repeated brief encounters with the same person are now considered close contact, according to a tweak to the U.S. CDC’s definition.

Previously, for somebody to be a “close contact,” they had to remain within 1.5 metres of you for a stretch of at least 15 minutes. The change recognises that, according to recent research, you don’t have to spend 15 minutes with the same person all at once. If you see the same person multiple times a day for a few minutes at a time, they are still considered a close contact if those encounters add up to 15 minutes.

Here’s the official definition as it stands today:

Someone who was within 1.5 m of an infected person for a cumulative total of 15 minutes or more over a 24-hour period* starting from 2 days before illness onset (or, for asymptomatic patients, 2 days prior to test specimen collection) until the time the patient is isolated.

That asterisk leads to a footnote longer than the definition itself, a sign that we are still in mostly-unknown territory when it comes to understanding how the coronavirus works. The CDC says the above definition is a reasonably good one if you’re looking for a concrete rule, but adds that plenty of other factors could be considered. You’re probably at higher risk if the person had active symptoms at the time, for example, or if they were up in your face rather than five feet away, or if they were shouting or singing.

We still don’t know how much protection masks really give us, and when you’re considering your contacts with people in your life, you may not realise that you — or the other person — may not be wearing a mask appropriately. For example, you might remember “oh yeah, that guy was wearing a mask,” but maybe it wasn’t fully covering his nose, or maybe it was wet, or made of a type of fabric that lets a lot of droplets through. For all those reasons, masks don’t factor into the “close contact” definition, even though they almost certainly do provide a good bit of protection.

Different organisations may have definitions that differ from the one the CDC uses. Gothamist reports that New York City’s benchmark is 10 minutes of close contact instead of 15, for example. The most important thing to know about the CDC’s rule change is that we have data that suggests shorter interactions add up.

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