In 2017, nearly 72,000 Americans died of an accidental drug overdose. Most of those deaths involved opioids. And despite growing efforts from public health officials, addiction advocates, law enforcement officers and more, fentanyl—a synthetic prescription painkiller 50 to 100 times more powerful than heroin—appears to be worsening the crisis, Rolling Stone reports.

In the past few years, reports of fentanyl infiltrating the heroin supply have skyrocketed across the country. Police say the super-potent opioid is being added to street drugs at nearly every level, and researchers in the field who have been testing drugs and examining the supply chain say it could soon replace heroin entirely.

Fentanyl has largely been blamed for a major uptick in overdose deaths over the past few years, as its potency means it’s nearly impossible to mix uniformly into street drugs. Just a few too many grains of the painkiller can cause even the most long-term drug users to overdose.

The switch from heroin to fentanyl makes financial sense to dealers. Currently, a kilogram of heroin costs about $200,000 on the street. A kilogram of fentanyl (which can be bought and sold online, imported from countries like China) costs just a few thousand dollars. Reports show that the two major Mexican drug cartels supplying drugs to the United States are cutting fentanyl into their heroin before sending it to the United States, at which point suppliers and street-level dealers often add more to help maximize their own profits. 

In New York City, advocates  say two thirds of the bags of heroin they’re testing are showing up positive for fentanyl. In Philadelphia, some bags have contained only diluted fentanyl.   Fentanyl also appears to have infiltrated the supply on the West Coast for the first time—an alarming development for local advocates.

In response, many state and local governments are turning toward public health campaigns aimed at harm reduction. Instead of telling drug users to stop, these programs instead suggest best practices for staying safe in the midst of the crisis—urging drug users to use clean needles to prevent the spread of hepatitis C virus (HCV) and HIV and to carry naloxone kits to reverse overdoses when they occur. Some clinics also offer fentanyl testing strips to help drug users determine what they’re injecting before it’s too late.

Meanwhile, police have been ramping up their efforts to zero in on dealers mixing fentanyl into their supply. But with so much drug use and cheap fentanyl on the market, it’s become an increasingly daunting task.