On Thursday, 41 scientists published the first worldwide analysis of a fungal outbreak that’s been wiping out frogs for decades. The devastation turns out to be far worse than anyone had previously realized.

Writing in the journal Science, the researchers conclude that populations of more than 500 species of amphibians have declined significantly because of the outbreak — including at least 90 species presumed to have gone extinct. The figure is more than twice as large as earlier estimates.

“That’s fairly seismic,” said Wendy Palen, a biologist at Simon Fraser University who is a co-author of a commentary accompanying the study. “It now earns the moniker of the most deadly pathogen known to science.”

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Scientists first noticed in the 1970s that some frog populations were declining quickly; by the 1980s, some species appeared to be extinct . The losses were puzzling, because the frogs were living in pristine habitats, unharmed by pollution or deforestation.