It's known on the street as China White, Dance Fever, Murder 8, and Jackpot.

An Ohio addiction doctor calls it "terrifying," a county coroner labels it "overwhelming," and the Columbus health commissioner says "it's very sobering."

Many Ohioans know the powerful painkiller fentanyl as a cold-blooded killer that preys indiscriminately on addicts, rich and poor, urban and rural. And most of them never knew what killed them.

Fentanyl, a synthetic opioid, is cheap, simple to make, easy to buy and 50 times more powerful than heroin. It is rapidly eclipsing heroin as Ohio's most vicious killer.

Portage County saw a number of drug users die last year as a result of ingesting a deadly mix of illegal drugs tainted with the synthetic painkiller fentanyl and the veterinary tranquilizer carfentanil. There were 47 unintentional drug overdoses in the county last year, 24 of which were directly attributed to fentanyl toxicity, a combination of fentanyl and other drugs, or carfentanil.

Headway was made in the fight against heroin deaths, with fewer people in Portage County dying as a direct result of its use -- though the synthetic additives commonly found mixed with the notorious drug are increasingly killing addicts, the Portage County Coroner's Office warned.

Overdoses statewide are shooting up, mostly because of fentanyl, and when the tally is complete, likely will top 4,000 for 2016 -- a 30 percent increase over 2015.

Beth Carey isn't sure what killed her identical twin sister, Chrystina Carey, on Feb. 22, 2013. The Marion woman's death certificate lists "morphine," the drug that fentanyl, heroin and similar drugs break down into once in the body. Only recently have coroners begun testing specifically for fentanyl and the even more powerful carfentanil, an animal tranquilizer.

The twins were born Feb. 28, 1982. They barely knew their mother, who was an addict and prostitute. She went out for a pack of cigarettes and never returned, leaving her daughters to be raised by their grandmother. The twins grew up inseparable, bonded by the absence of their mother and a father they never knew.

But unlike Beth Carey, she said her sister turned to drugs, "first starting with ecstasy then oxycontin. She moved on to heroin and was probably using drugs for eight years." Miraculously, Chrystina's baby, Jazlen Harden, was born healthy even though her mother used heroin throughout her pregnancy. Chrystina overdosed multiple times, but was brought back by use of naxolone, a life-saving drug that kicks people out of overdoses.

Carey said her sister's addiction was "bigger than us. She lived by doing drugs."

After spending several months in jail, and being forced to kick the drug habit, Chrystina shot up shortly after being released from jail.

It was just a few days before their 31st birthday when Beth got the call from Marion police. Her sister was dead.

"I had seen her decline. I knew her struggle and demons with her addiction," she said. "I was no longer a twin."

Beth Carey is now raising Jazlen, who is 5. Beth tells her she has two mommies, including her "mommy in the sky."

The National Institute on Drug Abuse says that legal fentanyl is available via injection, a skin patch, lozenges or a lollipop. However, illegally produced fentanyl comes as a powder or spiked on blotter paper. Dealers commonly mix fentanyl with heroin, marijuana and other drugs, in part because fentanyl is so cheap.

Treatment is available, but fentanyl is so addictive and deadly that many "people aren't making it to treatment," said Shawn D Holt, president and chief executive officer at Maryhaven, a Columbus drug and alcohol treatment center. Maryhaven treated 11,000 people in central Ohio last year, and 80 percent were addicted to opioids.

Holt said he recently asked his staff for the relapse rate for fentanyl users. "I was told there was none because people are dying," he said.

The stories from across Ohio about overdose deaths are legion. Among them:

Strapped in her car seat, 14-month-old Annabelll Sagstetter died in 2015 after her mother brought her into a Hilltop drug house, where she was exposed to a lethal combination of heroin and fentanyl. "I will never forgive myself," Erica Barley, of Reynoldsburg, told a Franklin County judge who sentenced her to five years in prison for involuntary manslaughter. "Deep into my addiction, I thought she was safest with me. I never thought this could happen. Now, after being sober, I know that bringing her there put her in danger and caused the worst possible tragedy."

Courtney A. Halye and Brian Halye died in March of suspected drug overdoses involving fentanyl or heroin. Their bodies were found by their four children in the bedroom of their Centerville home, south of Dayton. Mr. Halye was an airline pilot.

Denise N. Dickinson and Kyle R. Black were sentenced to prison on involuntary manslaughter charges in the death of their 11-month old son, Dominic. The baby died in 2015 from what turned out to be "acute intoxication of heroin and fentanyl." The child somehow ingested the drug while in bed with his parents who had used the heroin-fentanyl combination.

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Dr. Jon Sprague, a professor at Bowling Green State University and director of Attorney General Mike DeWine's Center for the Future of Forensic Sciences, said fentanyl has been around since 1960 when it was invented as a painkiller for use in cardiac surgery.

"It's a very potent pain relieving substance that unfortunately produces euphoria," he said. Like other opioids, Fentanyl reduces the output of a drug that sends out pain signals from the brain, while also stimulating the release of dopamine, the chemical that creates euphoria.

Fentanyl's potency can cause respiratory depression, coma and death. Even a dose of micrograms, the size of a grain of salt, is potentially fatal. That is why law enforcement, prosecutors and lab technicians are now wearing protective hazardous material suits when handling it.

Sprague said the drug is cheap to make, with ingredients costing $358 producing fentanyl with a street value of $18,000.

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Dr. Shawn Ryan, president of Brightview, a Cincinnati drug-addition treatment center, and president of the Ohio Society of Addiction Medicine, said that 90 percent of patients he treats for opioid disorders recently have used fentanyl.

Using a combination of medical, psychological and social treatments, Ryan said his patients have a 70 percent chance of kicking the drug habit.

The rush of fentanyl has "demonstrated the inadequacy of our treatment system," Ryan said. "Gov. (John) Kasich and our state leaders have done more than most states ... but what if we hadn't given out that Narcan? What wouldn't have happened if medicaid hadn't been expanded?"

Orman Hall, analyst with the Ohio High Intensity Drug Trafficking Area, said that fentanyl's potency makes it go farther with drug dealers. A kilogram (2.2 pounds) of heroin breaks down into 10,000 doses on the street, but the same amount of fentanyl would make 500,000 doses.

A key to fentanyl's addictive nature, Hall said, is the relatively short duration of its euphoric effects. While a heroin user can stay high on a single dose for an average of three hours, the high from a dose of fentanyl last only about 45 minutes. A shorter, more powerful high means the addictive craving returns far more often, resulting in more trips to the drug dealer.

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Fentanyl alone killed more than 1,000 Ohioans last year, and carfentanil was responsible for 174 overdoses in Cincinnati alone in a six-day span according to Sen. Rob Portman, who has introduced a bill that aims to keep the drug from flooding in from other countries, such as China and India. Many are shipped through Canada into the U.S.

Portman said that while private carriers such as UPS and FedEx require electronic advance data -- including who and where the package is coming from, who it's going to, where it's going and what's in it -- the U.S. Postal Service does not.

His bill, co-sponsored by Sen. Sherrod Brown and sponsored in the House by U.S. Rep. Pat Tiberi, R-Genoa Township, would require the U.S. Postal Service to also require electronic advance data, ideally enabling Customs and Border Patrol to target possible illegal packages. Brown, meanwhile, has introduced a second bill that would provide $15 million to help give Customs and Border Patrol additional tools to detect fentanyl being shipped in from overseas.

"It will put a huge dent into it and help a lot," said Tiberi of the Portman bill. "It's a piece of a tool to deal with drug traffickers."

Beyond that is a need for more people to understand the deadly consequences of even getting near fentanyl.

"If people knew where these drugs were really coming from, they'd never, ever use these things," said Peter Pitts, a former FDA associate commissioner who is now president and co-founder of the Center for Medicine in the Public Interest.

Dispatch Washington reporter Jessica Wehrman and Record-Courier reporter Dave O'Brien contributed to this story.