Hi and welcome to COVID Quickly, a scientific American podcast series.

This is your fast track update on the COVID pandemic.

We bring you up to speed on the science behind the most urgent questions about the virus

and the disease.

We demystify the research and help you understand what it really means.

I'm Tony Lewis.

I'm Josh Fishman.

And we're scientific Americans, senior health editors.

Today, we'll explain the new official methods to determine if you're in a pandemic safe zone

or a danger area.

Then we'll discuss what other pandemics look like when they were ending and whether this one

at long last is heading down a similar path.

The map of the US shifted last week or at least the map of COVID danger did.

Suddenly, a lot of hazardous regions were deemed safer.

What happened, Josh?

Did COVID disappear?

It was a weird moment, Tonya, and no, COVID hasn't gone away.

But last Friday morning, people looked at an official Centers for Disease Control map

showing much of the nation was in a high risk area.

And the next day, that map showed about 60% of the US was really at low or medium risk.

And people in those areas didn't need to wear a mask anymore, the agency said.

What happened was three things.

...