An epidemic of severe and rapidly progressive black lung disease is emerging among coal miners in Appalachia. Case counts from just three clinics in the region reveal the highest disease levels that doctors have ever reported, according to a study published in JAMA this week.

Between January 2013 and February 2017, researchers at the National Institute for Occupational Safety and Health documented 416 coal miners with the condition. Prior to the discovery, researchers largely thought that black lung cases were a thing of the past. Diagnoses have been rare since the late 1990s

The clinics, run by Stone Mountain Health Services, would typically see five to seven cases each year, Ron Carson, who directs Stone Mountain's black lung program told NPR. Now, the clinics see that many in two weeks, he said. And in the past year, they’ve diagnosed 154 cases.

“That’s an indication that it’s not slowing down,” Carson said. "We are seeing something that we haven’t seen before.”

In the study, co-authored by Carson, researchers also noted that the disease is more severe than in the past. Many of those diagnosed had worked in the mines for less than 20 years yet had severe, rapidly progressing disease. “Miners are dying at a much younger age,” Carson said.

According to an investigation by NPR, the skyrocketing case numbers and increasing disease severity may be due to longer shifts and mining thinner strips of coal, which can create more dust.

Black lung is caused by exposure to coal dust. The dust builds up in the lungs and causes inflammation, fibrosis, and eventual tissue death. The disease is fatal and can only be cured with a lung transplant.

In 2016, new federal protections for coal miners were fully implemented. These included decreases in allowable dust levels as well as improved dust monitoring. The authors of the new study note that they’ll need more case surveillance in the future to determine if these protections are effective.

JAMA, 2018. DOI:10.1001/jama.2017.18444 (About DOIs).