A coronavirus outbreak on Mount Everest has infected at least 100 climbers and support staff, according to an expert climbing guide.

The estimate by Lukas Furtenbach of Austria comes amid official Nepalese denials of a Covid-19 cluster on the world’s highest peak.

Mr Furtenbach, 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,” Mr 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.

He said it was obvious there were many cases at the Everest base camp because he could visibly see people who were sick, and could hear people coughing in their tents.

A total of 408 foreign climbers were issued permits to climb Everest this season, aided by several hundred Sherpa guides and support staff who have been stationed at base camp since April.

Nepalese mountaineering officials have denied there are any active cases this season among climbers and support staff at all base camps for the country’s Himalayan mountains.

Mountaineering was closed last year due to the pandemic.

Nepalese officials could not immediately be reached for comment on Saturday. Other climbing teams have not announced any Covid-19 infections among their members or staff.

Several climbers have reported testing positive after they were brought down from the Everest base camp.

Mr Furtenbach said most teams on the mountain were not carrying virus testing kits, and that before his team pulled out, they had helped conduct tests and had confirmed two cases.

Most teams are still at base camp, hoping for clear weather next week so they can make a final push to the summit before the climbing season closes at the end of the month, Mr Furtenbach said.

In late April, a Norwegian climber became the first to test positive at the Everest base camp. He was flown by helicopter to Kathmandu, where he was treated and later returned home.

Nepal is experiencing a virus surge, with record numbers of new infections and deaths. China last week cancelled climbing from its side of Mount Everest due to fears the virus could be spread from the Nepalese side.

Nepal reported 8,607 new infections and 177 deaths on Friday, bringing the nation’s totals since the pandemic began to more than 497,000 infections and 6,024 deaths.