The rise of the more potent fentanyl in its place has put a generation of older users, who had managed their addiction, at far greater risk of overdose. Abby Goodnough of The New York Times investigates.

Heroin has ravaged this city since the early 1960s, fuelling desperation and crime that remain endemic in many neighbourhoods. But lately, despite heroin's long, deep history here, users say it has become nearly impossible to find.

Heroin's presence is fading up and down the Eastern Seaboard, from New England mill towns to rural Appalachia, and in parts of the Midwest that were overwhelmed by