THURSDAY, March 29, 2018 (HealthDay News) -- Drug overdose deaths continue to pile up in the United States, driven largely by the opioid epidemic and the emergence of dangerously potent synthetic opioids like fentanyl, a new government report shows.

Overdose deaths increased by 21.5 percent in 2016, a much sharper spike than the 11.4 percent increase seen the previous year, researchers from the U.S. Centers for Disease Control and Prevention reported.

"The problem isn't just getting worse, it's getting exponentially worse," said Emily Feinstein, executive vice president of the National Center on Addiction and Substance Abuse.

"What's happening in our country is shameful. Addiction is a preventable and treatable disease. We know what to do, but we are not doing it. We are taking half-measures and expecting better results," added Feinstein, who was not involved with the new study.

Drug overdoses killed nearly 64,000 Americans in 2016, with two-thirds of deaths involving a prescription or illicit opioid, according to the researchers, who were led by CDC epidemiologist Puja Seth.

Recent increases in overdose deaths have been fueled by a continued surge in deaths involving synthetic opioids like fentanyl, which is 50 to 100 times more potent than morphine, the CDC scientists said.

In fact, overdose deaths related to synthetic opioids more than doubled between 2015 and 2016, the researchers found.

In what was one of the first high-profile overdose deaths involving fentanyl, a toxicology report obtained by the Associated Press this week showed that musical icon Prince had an "exceedingly high" concentration of fentanyl in his body when he died. Prince was 57 when he overdosed alone in his Paisley Park estate on April 21, 2016.

Drug dealers often cut heroin with the less expensive fentanyl, and unaware users risk overdose due to the potentially lethal potency of the synthetic opioid, said Dr. Robert Glatter, an emergency physician with Lenox Hill Hospital in New York City.

"What's clear is that many people are unaware that they may be risking their life when they think they are simply buying heroin to support their ongoing prescription drug habit," Glatter said. "People who use heroin should realize that fentanyl could be a potential contaminant which significantly raises the possibility for overdose and death."