Sea stars return to California after devastating die-off

Yes, but: This is just one area, and this doesn't mean the disease is gone. A major outbreak is happening in the Salish Sea in Washington, and the disease appears to be persisting at low levels from North/Central California up through British Columbia.

Some good news: Across the coast, there's been an abundance of baby sea stars. This 'pulse', first identified a few years ago, appears to be growing, per a September report by UC Santa Cruz researchers. Although some juveniles show signs of the disease, researchers hope they'll prevent the populations from collapsing.

The history: Sea Star Wasting Syndrome first appeared in ochre stars off the coast of Washington in 2013, and spread to several species up and down the West Coast by 2015. Die-offs like this have happened in past decades, but only in isolated areas. There's never been a coast-wide die-off before.

What's happening: So far, scientists don't know if the disease is caused by a virus, a bacteria, or a combination thereof. Anecdotally, some sea stars seem to do better when treated with antibiotics, but that could be because virus-caused lesions are prone to infection. A USGS study found the illness was caused by something virus-sized, and other research has implicated densovirus.

Go deeper: The University of California, Santa Cruz maintains a database of sea star die-offs and issues reports several times a year.