But when starfish started to die en masse in the Atlantic and the Pacific oceans last year, scientists took notice. What came to be called “sea-star wasting syndrome” (SSWD) was turning starfish to goo. Their deaths, which included slow detachment of their arms, have not been pretty.

“The whole arm is flat,” Drew Harvell, a Cornell University professor of ecology and evolutionary biology who studies marine diseases, told PBS. “It looks dried out, wasted, thin, deflated. Sea stars are not supposed to look like that. … My expectation is that within the next month all of the stars will die.”

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It was hard to say what caused the devastation — or what it presaged. Scientists were reluctant to blame global warming, but thought it could be a factor.

“These kinds of events are sentinels of change,” Harvell told The Washington Post’s Darryl Fears. “When you get an event like this, I think everybody will say it’s an extreme event and it’s pretty important to figure out what’s going on.”

Scientists still haven’t figured how to stop the plague — or how it kills starfish — but they may have figured out what is causing it. In a study published in the Proceedings of the National Academy of Sciences, researchers blamed SSWD in the Northern Pacific on a virus whose transmission may be facilitated by climate change.

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“Over this winter I surveyed here, and looked at every animal and there was no disease at all,” said Morgan Eisenlord, a PhD student in Harvell’s lab who participated in the study. “When we came back in the spring we found sick animals so it obviously spread as it started to get warmer” — though one researcher not involved in the study told the Associated Press that specimens were gathered in Oregon when ocean temperatures were colder than normal.

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Researchers isolated the virus in the lab and were able to infect healthy starfish with it. They said the disease may spread through the water when starfish gather together, or when they feed. And though scientists called the observation anecdotal, starfish in a lab fed mussels gathered from the ocean contracted the disease, but starfish fed frozen squid did not.

Though the virus has been noted in starfish and other species, including sea urchins, from as early as 1942, previous starfish die-offs have not been as widespread. No one is sure what the environmental impact of SSWD will be.

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“It has an extraordinarily significant effect on the biodiversity of the entire community,” Carol Blanchette, a research biologist at University of California at Santa Barbara, told PBS. “Losing a predator like that is bound to have some pretty serious ecological consequences and we really don’t know exactly how the system is going to look but we’re quite certain that it’s going to have an impact.”

What’s clear: The warmer it is, the better it is for diseases.