A team of researchers has unearthed the origins of the lethal fungus believed to have killed off a third of frog species: the Korean peninsula.

A new study revealed that ground zero of the powerful skin fungus is East Asia, before humans inadvertently brought it to the rest of the world through trade and other global activities.

The study is published in Science on Friday, May 11.

A Frog-Killing Fungus

For decades, entire species of frogs have been disappearing from forests. The chytrid fungus, Batrachochytrium dendrobatidis or just Bd, is responsible for the extinction or near-extinction of over 200 amphibian species.

The fungus attacks the amphibians' skin, which they use to breathe and hydrate, eventually leading to heart failure. It can affect at least 695 amphibian species, although its effect on some is more severe than others. The disease is called chytridiomycosis.

"This is the worst pathogen in the history of the world, as far as we can tell, in terms of its impacts on biodiversity," Mat Fisher, coauthor and Imperial College London mycologist, describes.

Scientists believe the skin-attacking fungus has decimated a third of all frog species in the world.

Ground Zero

To find out more about the deadly pathogen, researchers sequenced 234 Bd genomes from around the world and discovered four lineages of the fungus.

One of the four lineages is found only in the Korean peninsula and this Bd features much more genetic diversity than the other sites, confirming that the region is ground zero of the killer fungus ravaging amphibian populations.

The expansion of the disease's range boomed during a period when intercontinental trade was being embraced 50 to 120 years ago.

The team believes that globalization facilitated Bd's worldwide circulation — and is currently ongoing with the active pet trade. Scientists found infected frogs and toads in pet stores in the United States, Mexico, and even Europe.

"[The pathogen's spread] could have happened from any one event, from the cumulative number of events, or maybe some big anthropogenic events like the Korean War," Simon O'Hanlon, lead author and Imperial College London researcher, explains.

What's Next?

Now that scientists are aware that it's humans who caused the spread of the killer fungus devastating entire ecological systems worldwide, it's time to figure out what to do to stop it.

For the researchers involved in the study, the global amphibian trade needs to be stopped completely.

"Our research not only points to East Asia as ground zero for this deadly fungal pathogen, but suggests we have only uncovered the tip of the iceberg of chytrid diversity in Asia," Fisher points out. "Therefore, until the ongoing trade in infected amphibians is halted, we will continue to put our irreplaceable global amphibian biodiversity recklessly at risk."

Earlier in 2018, another study found that frogs may be developing resistance to the fungus, but scientists say it's too early to point to recovery.