Many new cases tied to one man who took that train into the city.

And tonight, another major move.

The city asking residents who have recently traveled to any sort of hot spots around the world to self quarantine A.

B.

C's with Johnson from New York City Tonight.

Tonight, the number of Corona virus cases doubling in New York to at least 22.

Most link to a lawyer who frequently commuted out of Grand Central Terminal, one of the busiest train stations in the country.

The community spread dynamic is unpredictable and worrisome.

So we're watching carefully his case causing a remarkable ripple effect.

Health officials saying he spread the virus to his wife, their two Children, another family and the neighbor who all went on to infect others.

At least 18 people in all trace back to one man, a city now reporting more than 2700 people ordered to self quarantine.

Gillian Steinberg is one of them.

She teaches English.

It's our academy in the Bronx, where one of the lawyers Children attend school it's now shut down.

What is your biggest concern now?

As this outbreak spreads, I think that there are vulnerable populations who genuinely have to be worried for their physical health.

But he thinks that we just have to be careful not to overreact tonight.

Mayor de Blasio, telling Any New Yorker, recently returned from five hard hit countries to immediately self quarantine Governor Cuomo activating a statewide emergency operation center in Albany and two outposts in Westchester County.

What is going to happen is the number will continue to go up.

It must because we are continuing to test more and more.

And now a health care worker in New Jersey testing positive.

Ah, man in his thirties, recovering in the hospital, one of two cases in the Garden state with the virus spreading around the world, people now asking serious questions about whether it's safe to fly major airlines, waiving fees and canceling domestic flights.

Delta and Alaska Airlines, disinfecting and scrubbing down planes, especially those high touch surfaces and with Johnson outside that hospital in New York with that initial patient is still being treated, and with the mayor calling the situation worries him.

As we've mentioned here tonight.

Now the city taking several pre emptive steps to try to stop the spread in New York City.

David, the health commissioner, is now ordering all teachers, first responders and medical workers employed by the city of New York to be tested for the virus if they show any symptoms and there will be consequences if they don't comply.

David, All right, with Johnson again tonight with thank you.

We know many of you at home have questions on this.

So let's get right to Dr Jen after in our medical editor.

And she was here in Washington in the last 24 hours, part of that small group meeting with the vice president and Jen.

I know you're aware of this this very small study out of Singapore that looked at the rooms of patients, bedrooms and bathrooms of the patients.

It showed a significant amount of the current virus in the rooms when they tested.

This number got our attention.

87% of the surface is testing positive, somewhat alarming.

But then, after being disinfected, that was a bit reassuring.

It went down dramatically, David, showing that surface cleaning does work.

We don't know exactly how long this strain of Corona virus can exist and live on hard surfaces like glass and metal.

But from other Corona viruses, the range could be anywhere from two hours to nine days.

So in addition to how long it less on surfaces.

Jen, I know a lot of people have been asking, Can you catch it simply breathing in the air if someone coughs or sneezes near you?

We've tackled this before, but because so many people are asking, I just wanted to hit that again tonight.

Such a common question and it's really unknown.

There is a suggestion that 3 to 6 feet of distance is kind of your buffer area, but it is thought also the closer and longer the exposure, the greater the risk.

And Jen, just to button this up, you have said right here in the broadcast in last couple of nights.

Toe.

Wash your smartphones down.

That's getting a lot of pickup really in newspapers here in this country and around the world, because that's something that's changed in our culture since the last time we've seen one of these spreads.

That's probably the major hot spot, David, So wipe those phones down and wash your hands.

All right, Great advice.

Jen will see you right back here tomorrow.

Hi, everyone.

George Stephanopoulos here.

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