You're listening to Shortwave from NPR.

Here in the US, we are in the midst of a new surge of coronavirus cases, hospitalizations,

and deaths.

The surge, in part, is due to a very transmissible strain of the coronavirus.

We know now that the highly contagious Delta variant now accounts for more than 80% of COVID

cases in this country, and it appears to spread about twice as fast as the original strain.

The CDC now says everyone, vaccinated or not, should wear masks indoors in public spaces

if they're in an area where the coronavirus cases are surging.

Joining me today is science desk correspondent Alison Aubrey, hi Alison.

Hey there, Maddie, great to be here.

Talk to me a little bit about this guidance.

Back in May, the CDC said that fully vaccinated people could take off their masks in most

settings, but two things have changed.

The vaccination rates have slowed down, and the Delta variant keeps spreading.

And Alison, public health experts that you've been talking to have been advocating for

this change, right?

Yes, absolutely.

Many thought the decision to lift the mask mandate in this spring wasn't well thought

out, and that the CDC has been too slow to respond, as cases creep back up.

Here's Dr. Zika Manuel of the University of Pennsylvania.

The CDC's position on masks has been behind the April almost every step of the way.

And the announcement is seen by some people as the agency kind of playing catch up after

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