WILLIAM BRANGHAM:

It's hard to grasp the full scope and scale of the opioid crisis we're in the midst of.

The numbers are staggering. Almost half-a-million Americans have died in the last 15 years from an overdose, and the majority of those involve opioids. On average, 91 Americans are still dying every single day.

In that same period, the rate of addiction to opioids has shot up by almost 500 percent. And the availability of addiction treatment hasn't kept up at all.

So, how did we get here?

Most experts say this crisis began in the 1990s, when some doctors and medical associations argued that, for generations, their profession had ignored the problem of chronic pain, which had caused unnecessary suffering for millions of patients.

They started pushing the idea that pain be seen as the fifth vital sign, something to be checked as often as blood pressure, and treated accordingly.

At roughly the same time, the pharmaceutical industry, which was eager to boost sales of its new class of painkillers, like OxyContin, told doctors that these new drugs could be used without fear of their patients becoming addicted.

The industry even put out testimonial videos, like this one from Purdue Pharma in 2000.