Dr. Corinne Stern is a different kind of doctor.

Instead of helping sick patients get better, Stern’s job is to get to the bottom of what killed a person — by determining the cause and manner of death.

For more than 15 years, Stern has served as the county medical examiner in Laredo, Texas, investigating everything from freak accidents to violent crimes.

But in the last year, she began to notice a disturbing link to many of the bodies on her autopsy table.

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"Prior to 2021, it was rare for me to see a fentanyl death in this office," Dr. Stern told Fox News.

"Now, I would say at least half of my drug overdoses have fentanyl," she continued.

Dr. Stern certainly isn’t alone.

Perhaps no other profession is more involved in America’s unfolding fentanyl crisis than those tasked with investigating overdose deaths — the country’s coroners, forensic pathologists and medical examiners.

"These overdoses are impacting all ages," says Bobbi Jo O’Neal, coroner for Charleston County, S.C.

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"From old or young, teenagers, up into their 80s … all demographics," she said.

O’Neal also serves as president of the International Association of Coroners and Medical Examiners, a group that assists other industry professionals in honing their craft.

She said that colleagues across the country, from big cities to little towns, are seeing a growing number of counterfeit pills.

"It can say Xanax on the pill, or they have the coding — but they can be fake and they are actually fentanyl," explained O’Neal.

The Drug Enforcement Agency (DEA) say that four out of every 10 counterfeit pills that are tested come back positive for a potentially lethal dose of fentanyl, which is about 2 milligrams (about the size of 10-12 grains of table salt).

Officials say fentanyl has become a common ingredient, mixed in with other drugs because it’s cheap and fairly easy to come by.

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That’s an obvious problem, considering a small amount of the synthetic opioid can be deadly — and that people may be taking it unknowingly.

This is something mom Jennifer Talamantes learned the hard way two years ago.

"I never thought that my son would die from drugs or an overdose," she told Fox News.

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Jennifer’s son, Jacob, died after he took a Percocet that was laced with fentanyl.

He was just 25 years old. His mother says he wouldn’t have taken it if he had known what was in it.

"Now they are paying with their life, that one mistake," Talamantes said.

"One of those pills could just be the end of it."

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Last year, 66 percent of all drug overdoses in America were attributed to fentanyl, according to data from the Centers for Disease Control and Prevention (CDC).

Officials fighting on the front lines of this new drug war fear things could get worse before they get better. 

They say mass educational campaigns — warning people (especially children) about the dangers of fentanyl — are critical to helping curtail the problem.

Parents in America such as Jennifer Talamantes say the best advice is to be open and honest with your children — and make it crystal-clear that it only takes a single mistake.

"Let them know how lethal this is," begged Talamantes.

"Just one pill. One pill or one night of having a good time with your friends," she said.

That's a simple choice that can have forever consequences.