The epidemic, in hard-hit Texas and across the country, appears to be waning.

A Dallas teenager's death from a lung injury associated with vaping comes at a time when hospitalizations for the mysterious disease are on the decline nationwide.

The teenager is the first person in Dallas County to die of injuries related to e-cigarette use, according to Dallas County Health and Human Services.

Dr. Philip Huang, director of the county's health authority, called the death "tragic" and cautioned that even short-term use of e-cigarette products can cause "severe lung damage, and even death." The teenager also suffered from a chronic underlying medical condition, according to the county's statement.

This is the second reported death in the state. The first was an elderly woman who died in early October, also in North Texas.

Texas has been one of the states hit hardest by the epidemic. As of late December, it had 228 confirmed or probable cases. Illinois is the only other state to report more than 200 cases, according to the Centers for Disease Control and Prevention.

More than 50 of these cases occurred in Dallas County, where hospitalizations peaked in late summer and have been dropping since, reflecting a nationwide trend.

Dallas County Health and Human Services

In a paper published in late December, CDC researchers analyzed emergency rooms' intake data from across the country and found that the number of reported cases peaked in mid-September. But the researchers cautioned that it was unclear if the data "represents a decrease in active case-finding by states or a true decrease in the incidence of cases."

In an email, CDC smoking expert Dr. Brian King wrote that he was confident that incidents of vaping-related diseases are declining.

But, he added, "Although we are seeing progress in the investigation and response, we must remain vigilant.”

There have been more than 2,500 vaping-related hospitalizations nationwide.

Vape pens — small electronic devices used to inhale highly concentrated liquids infused with nicotine or THC — were once conceived as a safer alternative to cigarettes. They are now considered a public health crisis, as they've exploded in popularity among school-age children, many of whom become unknowingly addicted to nicotine.

It's led the CDC to issue dire warnings, calling the devices "unsafe for kids, teens, and young adults."

Vape pens — small electronic devices used to inhale highly concentrated liquids infused with nicotine or THC — were once conceived as a safer alternative to cigarettes. They are now considered a public health crisis. Facebook

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Texas lawmakers raised the legal age to purchase vaping products to 21 last year, but that hasn't stopped teenagers from getting their hands on the products. Nearly half of patients with reported cases in Dallas County have been under 21, and a national survey found that 1 in 4 high schoolers had vaped in the last month. Coppell Independent School District has reportedly installed secret "vape detectors" to catch students who smuggle the devices — which can be as small as a thumb drive — onto its campuses.

The vaping-related lung disease epidemic has brought more attention to the problem. Researchers have linked the disease to vitamin E acetate, a common additive in THC vaping liquids found on the black market. But some patients with the disease reportedly used only legally obtained e-cigarettes, such as those manufactured by Juul.

President Donald Trump had promised to ban vaping cartridges with flavored nicotine, which studies have shown are particularly popular among children. Those restrictions went into effect Thursday, but with significant loopholes for "open-tank" systems as a result of lobbying from the vaping industry.