Dr. Richard Kock was on duty at Londons Royal Veterinary College in January 2017 when he received an urgent message from international health officials. He was needed for an emergency response mission in the Mongolian countryside, where a deadly viral outbreak was underway.

He packed his things, caught a flight to the capital city of Ulaanbaatar and drove for two days into the arid steppe. He found a disturbing scene: frozen corpses scattered on hillsides, burn pits stacked with bodies and residents addled with anxiety.

But this pandemic was not targeting humans. It was goat plague, a lethal and highly infectious virus that has killed goats, sheep and other small ruminants in huge numbers since it was first detected last century. There is a vaccine, but its application in Mongolia had been botched. The virus had spilled from domestic livestock into local populations of critically endangered saiga antelope, and it wiped out about 85% of the infected, Kock said.

Nearly everything died across a huge landscape, said Kock, who has worked for decades to stem infectious diseases around the world. There are only a few thousand saiga antelope left in Mongolia today, largely due to the goat plague.

The only comforting element of this tale is that the disease is not transmissible to humans. At least, not yet.

But Kock worries. Goat plague is a paramyxovirus, a virus in the same family as measles. Its case fatality rate can be as high as 90%, and some animals that contract it can infect eight to 12 others.

They are nasty viruses, Kock said, adding that theyre formidable in their spread and aggressiveness. It wouldnt take a big tweak in the goat plagues genome just two amino acids, essentially for it to become infectious to humans, he said. In theory, it is very possible.