The number of deaths from overdoses of illicit opioids rose sharply again in 2015, the Centers for Disease Control and Prevention announced Thursday.

“The epidemic of deaths involving opioids continues to worsen,” said CDC Director Dr. Tom Frieden said. “Prescription opioid misuse and use of heroin and illicitly manufactured fentanyl are intertwined and deeply troubling problems.”

Overdose deaths (9,580) from synthetic opioids, most of them fentanyl related, skyrocketed by 73%. Deaths that involved prescription opioids (17,536) rose just 4%.

And deaths attributed to heroin (12,990) went up 23% in 2015.