For more than 40 years, a mysterious disease has been appearing intermittently in populations of sea stars — also called starfish — causing massive die-offs and then disappearing again, sometimes for years at a time. Known as "sea star wasting syndrome," the disease continues to stump researchers, who have yet to identify a definite cause despite decades of research. Progressing from white lesions that appear on the limbs of affected individuals, the disease causes sea stars to disintegrate and waste away over the course of a week or less, their bodies sometimes physically tearing apart. The mortality rate is estimated to be around 95 percent.
Outbreaks of the illness have appeared sporadically since the 1970s, affecting both coasts of North America as well as the Mediterranean. It was observed in June 2013 in about 20 percent of the Humboldt County sea star population, but appears to have grown significantly worse since then.

Sea star wasting syndrome epidemic along the coast