Some climbers there have now reported testing positive, despite the Nepali government saying there are no infections on Everest.
Erland Ness, a Norwegian climber who was evacuated from Everest Base Camp in late April, confirmed to CNN he tested positive on arrival at a hospital in Nepal's capital, Kathmandu.
"When I tested positive, it was a shock. And then I realized that the expedition was over for me," Ness said. "My dream was to reach the summit and see the view."
Since then, Polish climber Pawel Michalski said in a Facebook post that "30 people have already been evacuated" from base camp and subsequently tested positive. And Everest ER, a voluntary organization that provides aid to those on the mountain, has said some climbers are isolating in their tents, "as we've had a few confirmed cases of Covid with evacuation from EBC (Everest Base Camp)."
Nepali government rules preventing mountaineers from sharing photos of other climbers without consent have restricted information coming from the mountain, but rumors are spreading of more cases -- and not just on Everest.
Sources tell CNN there are now dozens of suspected cases of Covid-19 at the Everest Base Camp - although officials deny it. CNN's Kristie Lu Stout
speaks to a Norwegian mountaineer who developed Covid-19 symptoms while climbing the mountain.
At least 19 people have been evacuated from climbing camps on the world's seventh-highest peak -- Dhaulagiri -- 345 kilometers (214 miles) west of Everest, according to Mingma Sherpa, chairman of tour operator Seven Summits Trek.
Seven tested positive and 12 others were due to take a test after showing symptoms, he added.
Nepal Army spokesperson Brig. Gen. Shantosh Ballave Poudyal said three cleaners at Dhaulagiri Base Camp have tested positive. One was evacuated Wednesday and two will be evacuated once the weather clears.
Lukas Furtenbach, an expedition leader, said climbers are worried Nepal will close Everest and popular trails.
"My guess is there will be more cases," Furtenbach told CNN from his camp at Mera Peak, south of Everest. "Everyone is concerned about a message coming from the Department of Tourism: 'You all have to go home.'"
Everest's patient zero
Nepal's economy relies heavily on tourism revenue, generating Rs 240.7 billion ($2 billion) in 2018, according to the World Travel and Tourism Council. Would-be climbers must obtain a permit from the Nepal Tourism Board in Kathmandu, which cost about $11,000.
Many Nepalis depend on tourism -- and climbing -- for their livelihoods. In 2018, Nepal's tourism industry supported more than 1 million jobs directly and indirectly.
After canceling last year's climbing season due to the pandemic, Nepal's Tourism Department granted 408 permits to Everest climbers this year -- up from 393 in 2019 when overcrowding, several deaths and a viral photo of mountaineers lining up to reach the summit drew international attention.
But far more than 408 people will be filing through base camp and up the mountain, given the vast entourage that climbers require. Chefs, guides and sherpas accompany each team, complicating attempts to bubble and socially distance.
"Base camp is really a small city," said veteran Everest watcher Alan Arnette, who summited the peak in 2011 and now runs a climbing website. Furtenbach estimated there are around 1,200 people at the camp this year.
Those conditions make social distancing difficult. "Normally there's a lot of socializing, events, base camp parties, and teams are visiting other teams and making new friends," Furtenbach said.
Now, most operators are attempting to remain in bubbles, with some sherpas and local staff having to forgo their usual routine of going home on rest days. And many teams have gone to great lengths to spend as little time on Everest as possible.
Tents at Everest base camp on Monday.
Prakash Mathema/AFP/Getty Images
"We all used hypoxic tents at home, we sent them to the clients, and they simulate the oxygen level of higher altitude," explained Furtenbach, who hopes to get up and down Everest in under four weeks.
The virus can strike quickly. Ness -- who became the first Covid-19 case on Everest to publicly identify himself -- said he started to feel weak after five days of his team's trek toward base camp.
"I felt weak, (and) I'm used to feeling strong ... (I had) a headache in the mountain, maybe a little bit fever, I'm not sure, but my oxygen level was very low."
"In base camp I was getting worse day by day," Ness said, adding that doctors eventually called for him to be taken to hospital, where he tested positive.
The positive result scuppered three years of training for Ness, but he considered himself lucky for a quick recovery.
"I think if I had got Covid in Kathmandu, I would not be very sick -- because I recovered so fast after leaving the mountain," he said. "But it's obviously worse to get Covid 5,500 meters (18,000 feet) [above sea level] than in Kathmandu."
'Erring on the side of panic'
Reports of Covid-19 cases have led to a tense atmosphere at Everest Base Camp.
"We're getting emails from people on other teams, trying to decide whether to go home, because it seems clear that things are getting quite serious," said Adrian Ballinger, an expedition leader who pulled out of the Everest climbing season over Covid-19 concerns.
"I'm hearing from guides, sherpas, and one of the helicopter companies about how many Covid rescues they're doing," he said. "I've had another major operator write me saying: 'You're so glad you didn't go.'"
As rumors swirl, concerns are also rising about a lack of on-site testing. "We would expect that the government (would be) confirming these cases, keeping everything transparent, maybe even sending a team to base camp to do a mass test which would find superspreaders," said Furtenbach, the expedition leader.
"I think every operator would be happy to pay for this -- it would probably save the season, because there is the risk if there's more and more cases that (there) could be an early end to this season."
Everest ER, an aid service run by the non-profit Himalayan Rescue Association, wrote in a Facebook post Tuesday that persistent coughs have been their number one complaint this season.
"This year it's especially challenging in light of the Covid pandemic," they said. "We do not have the capacity for rapid point of care testing at the moment."
Speaking about a Seven Summit Treks expedition at Everest, Mingma Sherpa said his team had set off from Camp 2 and were expecting to reach Camp 4 on Thursday. "If we conduct Covid-19 tests among the climbers, some of them may test positive for the virus. But none of them so far has shown any serious health complications except for common cold and coughs," he said.
Lukas Furtenbach as he begins his ascent of Everest.
Courtesy Lukas Furtenbach
Seven Summit Treks has 130 clients climbing Mount Everest this spring. The first summit bid led by the company is set for Sunday.
Multiple Everest climbers told CNN their teams are reluctant to talk to journalists about the Covid-19 situation, for fear of being rejected for climbing permits in future seasons -- making it harder still to estimate how many climbers have been infected, and ensuring the rumor mill is in overdrive, even among climbers.
"I know of people who have had it, who got infected, went to Kathmandu and now they're recovering, and I know other people who have not had one case in their camps," Arnette said, characterizing his conversations with climbers over recent weeks. "It's very, very spotty, and situational."
"All of us are trying to figure out what's going on, we're erring on the side of panic," he added.
The moral question
Of all the places in the world to catch Covid-19, Mount Everest may be the worst.
"Every single person's respiratory system is struggling, and is working in overdrive, and it's that much more susceptible to upper respiratory illness," said Ballinger, the expedition leader. He said climbers face an intense physical battle with each step up the mountain.
"You can't sleep at altitude, so you have this deep fatigue from days of not sleeping. You can't eat, because your digestive system is considered non-essential -- anything you put in your stomach, you become incredibly nauseous," he said.
Persistent coughs are so common on Everest they have a name -- the Khumbu cough, after the valley that leads to Everest -- making detecting Covid-19 particularly difficult.
"Your whole body is already working on its limits, so catching Covid would be a real threat to your health and even to your life," said expedition leader Furtenbach.
And evacuations can become perilous once teams have left base camp and begun their ascent. "If the weather's bad and someone's developing problems, evacuation without a helicopter would take days and it's very dangerous," Furtenbach said.
"So it would be a big problem if someone infected developed symptoms higher up the mountain."
For now though, morale is intact.
"Everyone's excited," Furtenbach said. "We've had clients waiting now for two years, and it's their life dream."
Furtenbach's team brought their own Covid-19 tests to Everest, and are regularly testing team members.
Courtesy Lukas Furtenbach
But with Nepal and neighboring India in the grips of a catastrophic second wave of Covid-19 infections -- Nepal reported its highest daily number of new coronavirus infections on Wednesday -- some climbers are also reckoning with a mental hurdle.
"I think we'll start to see some climbers leaving because they just feel that they're on the wrong side of the moral question, with the Kathmandu outbreak being so strong," Ballinger predicted. "They're sitting there with thousands of bottles of oxygen."
"If there are more and more cases coming in (at base camp), the authorities in Nepal will have to do something," Furtenbach added, again suggesting an early end to the climbing season is possible.
"I think they tried to do the right thing, they tried to save the season. But maybe it's not the right thing."
Correction: An earlier version of this story misspelled the name of the Nepal Army spokesperson. He is Brig. Gen. Shantosh Ballave Poudyal.