America's top expert on infectious disease, Doctor Anthony Fauci, Dr.

Fauci, thank you for your time this morning and for your tireless service over these last several weeks and years.

A CZ We heard from the president all last week.

He was hoping that we could reopen the country by Easter.

But of course, we saw that extension of the guidelines yesterday.

Take us inside that decision.

What convinced the president was necessary?

What convinced you?

Well, it was clear, George at the dynamics of the outbreak, what was going on in cities like New York City and Westchester and New Orleans and others was clearly still on an uptick.

And to pull back the mitigation methods before you reach the peak and turned and turned the corner, I think, really would have been imprudent, because that would have merely regenerated despite to go up.

So we had some intensive conversations with him, and we convinced them he listened.

And we said the better part of valor would be to extend them until the end of April, when we think it would peak and start coming down.

I mean, these are all projections.

But that thing we were pretty sure of is that if we prematurely did it, it would likely rebound.

And that's one thing you did not want to happen.

You talk about the peak at the end of April.

The president seemed to say yesterday that the models estimate the peak death rate in two weeks.

So So which is it?

Is it two weeks from now or the end of April?

Well, what he was saying that the number of deaths would probably peaked by a certain point.

But you still get a number of cases that go up, which will ultimately lead to less death rates because the cases anticipate the death rates.

What he was saying that we had such a surge earlier that within two weeks you've been out of a peek in the death rates.

The death rates start coming down, but you have another curve, which is actually the new infections.

So they're complicated curves that overlap each other, and and the death rate numbers are pretty stunning.

I mean, 100 to 200,000 lives could be lost.

Are you all estimating that even if these guidelines are extended.

Yeah, I mean, even if the's guidelines that extended, we will lose more people, exactly how many more we would lose is uncertain, depending upon the efficiency of the mitigation methods.

But clearly what you saw yesterday and the day before that within one day, we double the number of deaths mean it was just really very, very sobering.

It is over.

And of course, all of us here in New York or dealing with it.

New York has been described as the epicenter of this virus here in the United States right now.

What other areas air concerning you right now?

Well, certainly New Orleans.

George is in that area where it's worrisome because the spike and the peak and the dynamics of that curve starting to resemble a bit of New York.

It's a smaller city, obviously, so they can't be totally comparable.

But the dynamics of the outbreak in New Orleans a worrisome were also worried about Detroit.

Detroit is starting to show some signs that they're going to take off L.

A.

We worry about, even though they had an early start, they come down a little.

It looks like that they may have the opportunity and on the misfortune of spiking up.

And if you look throughout the country, there are a number of smaller cities that sort of percolating along a couple of 100 cases.

The slope doesn't look like it's going up, but what we've learned from painful experience with this outbreak is that it goes along almost on a straight line.

Then you have a little celebration celebration that it goes way, way up.

So we've seen that in New York.

Our European colleagues have seen it in Italy and France and Germany and Spain, and it's a rather consistent pattern.

It looks like it's low level, it starts to accelerate, and then it really goes up.

That's the thing.

We really gotta be careful of what we're gonna have all of these little mini outbreaks throughout various cities in our country.

Given that spread, I mean, the president said he hopes to have the United States well on our way to recovery by June 1st would not take extending these guidelines beyond the end of April.

You know, I think April might do it, George, but we kept an open mind when we presented it to the president.

We said 30 days is a solid.

I think we should do it.

15 days was too little.

None of us felt that 15 days was adequate.

And when he asked the obvious question, which is a reasonably good question, do you think is a possibility that we may be able to go best 30 days?

We said we didn't think so, but there's always that possibility, depending upon the efficiency and the effectiveness of the mitigation methods.

Finally, sir, what's your best hope right now for getting treatments on the market a CZ quickly as possible and a possible vaccine?

Well, we have a couple of clinical trials that are accruing now over 200 patients with one drug called route from Dez Silvia, a couple of other drugs and being tested in some in early stages of development.

I would think by early summer, late spring, we will get a signal in one of those drugs to see whether it works or not, and if it does, will widely distributed and if it doesn't, we'll just get it off the shelf, get it off the table because it won't be usable.

But we have the opportunity to prove one of Maura of them are actually working, and that's gonna be a matter of a couple of months.

Vaccine A little bit different, George, we're in the phase one trial.

We went into it as quickly as we possibly could, the fastest ever.

But still, the process at rocket speed takes about a year to a year and 1/2.

So if we cycle with this outbreak and it comes back next fall and winter, we might have the early the components of the vaccine ready to count two.

That outbreak likely next winter.

Dr.

Fauci, thanks for your time this morning.

Good to be with your judge.

You know, I hope all of our viewers understand Dr Fauci is history.

He is the definition of a public service.

He's been serving as the head of infectious disease since 1984 6 presidents and has always been a calm voice of reason and candor and science.

And he certainly has through this trying time.

Hi, everyone.

George Stephanopoulos Here.

Thanks for checking on 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 the download.

The ABC News After breaking news alerts.