Millions of starfish along the western coast of North America have been dying off from the destructive “sea star wasting syndrome,” whose previously unknown cause has now been discovered, researchers say. 

Researchers have identified the Sea Star Associated Densovirus as the cause behind the massive numbers of dead sea stars. This type of virus is reportedly common in invertebrates.

The Cornell Chronicle reported one researcher’s comments on the findings: “Not only is this an important discovery of a virus involved in a mass mortality of marine invertebrates, but this is also the first virus described in a sea star.”

The virus has been detected in samples from sea stars as far back as 1942. The cause for the current surge, however, is less clear. Reasons from sea star overpopulation to changes in environment to mutation of the virus were all offered up as possibilities.

Sea Stars play a significant part in their ecosystem, according to experts quoted by the Chronicle. The are “keystone” predator species that contribute to maintaining species diversity.

Given that the epidemic has been both spreading and intensifying, the revelation of its cause will hopefully aid scientists in responding to the widespread sickness.