system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why has heroin use suddenly exploded?

Why is there a "new heroin epidemic" in the past few years?  I understand it partly stems from pain pill abuse, such as oxycontin but how does that explain such a cheap supply?  Where is all the dope coming from? - Is it related to the Afghan conflict and the abundance of opium in that region?  Is something like Iran-Contra, but with heroin instead of cocaine suspected of going on?

Every day there's some story about heroin on the news: PSH, crocodil in Russia, etc.
gpt
I heard a discussion of this on NPR a week or two ago.  The belief is that there are two major factors:  
  
One is that there has been a big move in this country to reduce the amount of over-prescription of narcotic medicine - Oxycontin, Vicodin, etc.  So people who have become addicted to prescription pain pills are having a more difficult time getting them, and they cost more when they can be acquired.  
  
In concert with that, heroin has become very cheap, mostly due to the turmoil in the Middle East. There aren't a lot of good government controls in many countries preventing its production and distribution, so the production has gone up, driving prices down.  And there's a belief that some terrorist organizations are funding their operations through opiate production.    
   
The obvious choice for an opiate-seeker is therefore to switch to heroin. It is cheaper and more accessible.  Smart, huh?