In the 1970s and 1980s frogs and other amphibians seemed to be disappearing overnight. By 1999, researchers had determined the culprit was a deadly disease caused by chytrid fungus which infected the animals with tiny, swimming spores.

Today this disease, called Chytridiomycosis, is thought to be one of the deadliest pathogens on the planet. It infects hundreds of species of amphibians and is thought to have wiped out a third of all frog species. These animals are important contributors to biodiversity, insect and disease control and may even be sources of new types of medicine.

For decades, scientists hoping to save these semiaquatic animals from extinction have been trying and failing to pin down the origins of this mysterious killer. They knew it developed from a common ancestor, but couldn’t agree on where or when. Now, an international group of scientists has compared the genomes of 177 samples of the deadly fungus from six continents. They determined that the pathogen most likely arose on the Korean Peninsula 50 to 100 years ago and spread through global trade.

Their research, published Thursday in the journal Science, reiterates that the pathogen comes in many different strains, some more virulent than others. It suggests that new variations of the fungus can still develop and spread disease without proper protections.