Heroin Overdoses Killed More People in US Than HIV, Melanoma or Firearms in 2015

— -- The opioid epidemic continues to worsen in the U.S., with more people dying from heroin overdoses than firearm homicides, melanoma or HIV-related causes, according to data from the U.S. Centers for Disease Control and Prevention.

In 2015 at least 13,150 people died of heroin overdose, according to the CDC Wonder database, which houses public health data.

That number was higher than the number of people killed in firearm homicides in the same year, which was 12,974, or the number of deaths attributed to HIV, which was 6,465, according to the CDC database. It was also higher than the number of people killed by the most deadly form of skin cancer, melanoma, which the American Cancer Society estimated caused 9,940 deaths in 2015.

The staggering number of deaths related to heroin use is just a part of the toll of the opioid epidemic. In 2014, 28,000 people died from opioid overdoses -- which includes heroin overdoses -- and half were due to prescription drugs.

Dr. Caleb Alexander, co-director for the Johns Hopkins Center for Drug Safety and Effectiveness, said the heroin overdose numbers first highlighted by The Washington Post on Thursday, were "alarming" and showed the growing impact of opioid abuse in the U.S.

"Both heroin and illicit fentanyl are really complicating efforts to try and reduce opioid-related injuries and deaths," Alexander told ABC News today. Fentanyl is an opioid often made and sold illicitly that can be as much as 100 times more potent than heroin.

Alexander pointed out that what makes the problem more difficult is that addicts have multiple avenues to find and take opioids from prescription drugs to illicit substances like heroin or fentanyl or even veterinary opioids like carfentanil, which was designed to sedate elephants.

"There are a lot of different sources of this products," Alexander said. "The underlying things that fuel this is the vast number of Americans that is physically dependent or addicted to the product."