ATLANTA — New information on vaping is startling doctors across the country.

The Centers for Disease Control and Prevention said Friday that the number of cases of severe lung disease possibly linked to e-cigarettes has doubled, with more users getting sick every day.

Doctors are racing to find out why. What they do know is that the lung damage in those who are stricken is severe and possibly irreversible.

There is so much that doctors don’t know about the possible connections. They’re not even sure if the outbreak of lung illnesses is a new phenomenon or just newly recognized. They also don’t know if there might be some new additives in the products, which are used by millions of people.

The latest numbers released by the CDC show that more than 450 e-cigarette users in 33 states have developed lung illnesses that are possibly connected to vaping, including the 215 possible cases identified as of earlier this month. Two of the patients are in Georgia. Five people across the country have died.

RELATED: US health officials report 3rd vaping death, repeat warning

Health officials aren't sure what the users have in common other than that they all used vaping products -- often THC, nicotine, or both. It's also unclear what all of the ingredients are in the various commercial THC or nicotine products they are inhaling.

Most of the people stricken are once-healthy young people who may never recover.

On a conference call Friday from CDC headquarters in Atlanta, the CDC’s Dr. Dana Meaney Delman said researchers are racing against time.

“So far, no definitive cause has been established,” Dr. Delman said. “At this time, no one device, product or substance has been linked to all cases.”

RELATED: Health officials investigating 215 cases of lung disease possibly linked to vaping

RELATED: Georgia Department of Public Health investigating possible vaping-related illnesses

And the FDA’s Mitch Zeller warned not only against the potentially dangerous e-cigarette recipes that big corporations are marketing, but he specifically warned against homemade concoctions, as well.

“If you’re thinking of purchasing one of these products off the street, out of the back of a car, out of a trunk, in an alley, or if you’re going to then go home and make modifications to the product yourself using something that you purchased from some third party or got from a friend, think twice,” Zeller said.

The researchers say all they know is this--people who do not use e-cigarettes are not developing the types of severe lung damage that are inflicting increasing numbers of users.

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