KNOXVILLE, Tenn. — It's a story many of you are still talking about--the measles in East Tennessee.

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The CDC reports 695 measles cases in 22 states.

That includes one case in Tennessee.

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It's the largest number of cases since the U.S. declared measles eliminated in 2000.

The measles can be transferred through the air, and that's something hospitals have to combat with any airborne disease.

On the roof of East Tennessee Children's Hospital, there's a vent that you probably don't want to spend a lot of time around.

A biohazard sign sits on it.

Infected air from the hospital is filtered through a high-powered air filter and then pushed out the vent.

The air comes from places inside the hospital, like the sick waiting room.

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The rooms with sick patients have negative air pressure, which sends the air upward.

Just before it hits the outside it's filtered through the high-powered filter on the roof.

"It has to be filtered to make it safe," said Director of Emergency Services at East Tennessee Children's Hospital Christy Cooper.

It's just one-way Children's keeps the air clean around the hospital, especially for kids.

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"Infants are our most vulnerable population because they've not been immunized yet," said Cooper. "So they are at the highest risk for an infection like measles."

Cooper said they use those high-powered filters and air pressure to keep the air clean.

Places like the NICU are kept at a positive pressure compared to the hallway.

Air filters into the room and is pulled out in its own system, which creates an air barrier.

"The room is positive, so the germs don't come in from the corridor and other things," said Cooper.

She says the engineering team is constantly making sure the room pressures are correct.

"They have central monitoring, they have monitoring on each room, they do preventative maintenance to make sure the room is always ready to go for us," said Cooper.

She says patients can be safe knowing even the air is working to keep them healthy.

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"If we can keep that measles kid or another kid with some type of airborne thing out of the NICU, we work hard to do that," said Cooper. "Our doctors will see them in a different unit, and we provide care for them there so we keep this population as safe as we can."

Cooper said they have rooms throughout the hospital designated as positive or negative pressure to handle a variety of infections.

The Tennessee Department of Health says it has now received 211 calls to its hotline asking about measles.

The hotline started last Thursday.

Earlier this week, the department said an East Tennessee man who tested positive for the virus stopped at two gas stations in East Tennessee--one in Clinton and another in Chattanooga.

If you have any questions related to the measles, you can contact 865-549-5343