A coronavirus outbreak on Mount Everest has infected at least 100 climbers and support staff, an expert mountaineering guide said, giving the first comprehensive estimate amid official Nepalese denials that the disease has spread to the world’s highest peak.

Lukas Furtenbach of Austria, who last week became the only prominent outfitter to halt his Everest expedition due to virus fears, said one of his foreign guides and six Nepali Sherpa guides have tested positive.

“I think with all the confirmed cases we know now — confirmed from (rescue) pilots, from insurance, from doctors, from expedition leaders — I have the positive tests so we can prove this,” Furtenbach told The Associated Press in Nepal’s capital, Kathmandu.

“We have at least 100 people minimum positive for Covid in base camp, and then the numbers might be something like 150 or 200,” he said.