There’s been something of a renaissance of raw milk in recent years. And, not surprisingly, the dicey drink of bygone eras is also reviving disease outbreaks.

In recent years, researchers at the Centers for Disease Control and Prevention have noted that more states have made it legal to get raw (unpasteurized) milk and yearly outbreak numbers linked to unpasteurized dairy have quadrupled nationwide. Today, experts released an analysis of a 2016 multi-drug resistant infection outbreak in Colorado that highlights the growing problem of raw milk consumption—and the challenges that lie ahead. Specifically, the milk in the outbreak was consumed legally while health authorities were powerless to halt distribution even as they watched the outbreak play out over weeks.