Here's NBC's chief national correspondent, Matt Gutman.

Tonight, fear for the safety of health workers on the front lines after hundreds may have been unintentionally exposed to the virus in at least two medical conferences.

One in New York's Times Square bringing together hundreds of e R physicians and medical teachers.

This E R doctor Rose Knee Daniel says he felt symptoms after returning home to San Francisco and tested positive in an online post.

Daniel writing.

I avoided all handshakes, yet I still worry that I either picked up the illness there or, worse, exposed someone else.

He's now in isolation at home.

Lisa Merc is a nurse who also tested positive after attending a different medical conference in Hawaii with hundreds there, I just felt like extremely exhausted, tired I'm not 100% sure contracted every others on edge, waiting for answers.

Eight year old Adele is an isolation.

How have you been feeling?

Has been hurting, but that's all.

I've been pretty good design.

Her mother, Vida Tyson, called the Health Department hotline to get her tested when she had symptoms.

I call a different numbers and you spoke with eight different people.

And, um, they meant well.

And then they referred me back to the original number.

She gave up, but then she fell ill.

Went to the e r, got tested a week ago.

Still no results.

I don't know what I'm gonna be able to leave my house.

I don't know if I've infected a lot of people.

I can't tell anyone anything, because I don't know.

But many with the virus are holding up well, eh?

NBA player Donovan Mitchell still showing no symptoms.

If you were to tell me I'm not playing a seven game series tomorrow, I'll be ready to lose up.

Actor Idris Elba is isolating with his wife now.

The time for solidarity.

Now's the time to thinkin about each other at tonight.

Seven days after testing positive for the virus, Tom Hanks and his wife, Rita, released from the hospital posting a picture of the typewriter he brought with him a Corona, saying Role in this together flattened the curve, and we're now learning about a handful recovering through experimental treatment every morning and have a fever.

It was very, very, very tough to breathe.

Chris Kane's condition was deteriorating.

He was admitted to a Washington state hospital eight days ago.

The next day, he was given rendez severe medication, originally created for treating Ebola, but was unsuccessful for that.

It's now being given only to the sickest Corona virus patients, and he says it saved him.

I think within 48 hours I was feeling a lot that I think that rhythms of here gave the extra jump started a Kickstarter whatever I needed to kind of turn that corner.

That's actually hopeful news tonight, Mac up men live outside U.

C L.

A.

Medical center in Man.

I want to get back to that experimental treatment that you reported on here that seemed to help that patient in Washington state.

What are authorities telling you about it tonight?

David?

There It's one of several experimental drugs currently being tested.

Now this one is only being used in the most acute cases when there is no other alternative.

It's being used in several hospitals around the country.

Now there are clinical trials here in the U.

S.

And in China, but it could take months to determine if this drug is effective and only then, once approved, will be rolled out to the public.

David.

All right, Matt.

Thanks to you again tonight.

Hi, everyone.

George Stephanopoulos Here.

Thanks for checking out the ABC News YouTube channel.

If you'd like to get more video show highlights and watch live event coverage, click on the right over here to subscribe to our channel.

And don't forget to download the ABC News after breaking news alerts.

Thanks for watching.