For the first time since the early 1990s, drug overdose deaths are decreasing in the United States, a statistic that has many people hopeful that the opioid epidemic may be waning. But a new report from the think tank RAND warns of a potential spike in the crisis if fentanyl continues to move west, Vox reports.

The RAND study documents the rise of synthetic opioids like fentanyl, which are increasingly being mixed with (and sometimes entirely replacing) opioids such as heroin and painkillers in illegal drug markets. The synthetic stand-ins are much more potent than other opioids and are linked to an increased risk of overdose.

Fentanyl has largely infiltrated drug markets in the Northeast and Midwest. But recent reports out of San Francisco, Seattle and British Columbia suggest the potent drug is moving westward.

If that happens, warn drug researchers, the United States could see a “third wave” in the opioid epidemic, reversing the nation’s progress in the fight against opioid-related deaths. In fact, according to the same preliminary 2018 data from the Centers for Disease Control and Prevention that found overdose deaths were falling overall, synthetic opioid–related deaths increased from more than 29,000 in 2017 to nearly 32,000 in 2018.

The RAND report proposes steps the nation can take to help prevent a fentanyl crisis. For example, studies show increasing access to medication-assisted addiction treatments like methadone and buprenorphine can help reduce the death rate for opioid addiction patients by 50% or more. Efforts to better detect fentanyl at mail and shipping routes and at the U.S. border could also help cut back on its availability in the U.S. drug supply. Expanding harm reduction efforts, like increasing access to the overdose-reversing drug naloxone and opening up syringe exchanges, could also help.

The report concludes that as a new drug, fentanyl will require new modes of thinking about addiction and drug abuse, including controversial solutions such as making fake drug-selling websites to lure would-be buyers away from growing online markets for the drug, implementing prescription heroin programs and establishing supervised consumption sites.

“Limiting responses to small tweaks on existing approaches in the United States is likely to condemn many people to early deaths,” the report states.

To read the full report on Vox, click here.