A suspected ‘bad batch’ may have caused Baltimore drug overdoses. What does that actually mean?

 A decade ago, Baltimore saw a stretch of drug overdoses similar to the more than two dozen reported cases on a single day this week that spun up a frenetic response from law enforcement, medical personnel and harm reduction advocates.

It was the summer of 2015 and Baltimore’s health commissioner at the time, Dr. Leana Wen, heard from community leaders in a meeting about “bad batches” of drugs.