While the drug addiction and overdose epidemic engulfing the United States is widely known, less is known or understood about the deadliest drug involved in the crisis.

Fentanyl, a synthetic opioid pain medication similar to heroin, is the fastest-growing cause of overdoses in the country, according to The New York Times. The drug, hundreds of times more potent then morphine and 50-100 times more potent than heroin, is often mixed with its distant cousin unbeknownst to the user. Because the user is unaware of the potency of the drug, they will overdose considering that just two milligrams of fentanyl is considered a lethal dose.

Fentanyl was first created and used for medicinal purposes. It’s potency and efficiency made it one of the most popular prescription pain medications by 2012. Despite the epidemic and the illegal overflow of the drug into the U.S., fentanyl continues to be prescribed to patients in pain. But even when prescribed legally, overdoses are common as accidents with dosages are likely to occur.

Over the past few years, the country has seen a staggering jump in deaths occurring from overdoses. While the numbers are still being collected, it is expected that over 59,000 people died from drug overdose in 2016, the largest annual jump ever recorded. In addition, drug overdoses are now the leading cause of death among people under the age of 50. Fentanyl, because of its high potency and availability, is a major cause of the increase.

With the number of people dying from fentanyl so high, people in the public eye have died at the hand of drug as well. On April 21, 2016, Prince died after giving himself a lethal does of fentanyl. Paul Gray, the former bassist of Slipknot, died in 2010 of a fentanyl overdose as well. Prince and Grey overdosed in Minnesota and Iowa respectively, two states that have seen major upticks in fentanyl deaths in recent years.

While the fentanyl epidemic rages on, there have been very few steps taken to try and curb it. Recently, law enforcement officials have heightened their efforts to take down illegal fentanyl dealers who sell the drug online on the dark web – a surprising amount of fentanyl is shipped unknowingly by the postal service in the U.S. In addition, effected communities across the country have taken steps towards reducing drug addiction and overdoses by lobbying for more available rehabilitation for addicts.

Still, fentanyl continues to kill across the country. By the end of 2017, more than 65,000 people are expected to lethally overdose on drugs, 10,000 more people than died of car accidents in 1972, the year with the most car accident deaths ever recorded.