Organ transplants in the United States are on the rise for the fourth year in a row, according to new data from the United Network for Organ Sharing (UNOS). The influx of donors is the result of the rising death toll due to the nation’s opioid epidemic, St. Joseph Missouri’s Daily Star-Journal reports.

Specifically, the UNOS news release states that 33,606 organ transplants took place in the United States in 2016, marking an 8.5 percent rise from 2015 and a nearly 20 percent increase in organ donations since 2012. According to the Richmond, Virginia–based transplant organization, deaths related to opioid addiction accounted for nearly 50 percent of last year’s gain.

Meanwhile, the National Center for Health Statistics reports the number of U.S. deaths from opioids—including prescription painkillers, heroin and its more potent cousin, fentanyl—jumped from 28,647 in 2014 to 33,091 in 2015. According to transplant experts, those deaths translated to a 9.2 percent rise in the number of deceased organ donors between 2015 and 2016. 

Since opioids pass through a person’s system quickly after death and typically do not damage any particular organ within the donor, U.S. doctors are often able to salvage many viable organs from people who have overdosed. What’s more, experts say donors who die of opioid-related causes tend to be younger and healthier than other deceased donors, which means better-quality organs for those on transplant waiting lists.

In addition to the opioid epidemic, experts say the recent rise in organ transplants may also reflect physicians’ increased willingness to accept donors they may have rejected in the past. For instance, recent advancements in HCV testing, prevention and treatment have made it possible for U.S. patients on transplant waiting lists to skip ahead in line if they are willing to accept an organ from a hepatitis C virus (HCV) -positive donor.

However, the UNOS report also warns that although the rise in organ transplants is good news for the hundreds of thousands of people currently on U.S. waiting lists, more donors are desperately needed to meet demand. According to the nonprofit’s website, 118,978 people are still waiting for a lifesaving transplant.