KATHMANDU, Nepal—There are countless obstacles to reaching the summit of Mount Everest. Beyond the physically grueling ascent, climbers spend weeks at base camp getting acclimated to the altitude. They need time and money.

This year they had yet another hurdle that prevented many of them from reaching the top of the world’s tallest mountain: Covid-19.

More than 400 climbers from around the world and some 1,100 local Sherpa and support staff reached Everest’s base camp starting late March and through April, just as a terrible surge of Covid-19 was accelerating in India. It would eventually sweep through neighboring Nepal and get all the way to the base camp at 17,500 feet.

Some 40 to 200 people at the base camp were infected, according to varying estimates from a government official, climbers and expedition companies. None of them died from Covid-19, according to Gyanendra Kumar Shrestha, a government liaison officer who managed a team of 40 to 50 climbers at the base camp, although four people—two Sherpa staff and two foreign climbers— have died on their expeditions.

Still, the threat from Covid-19 was enough that some expedition companies pulled out. Austria-based Furtenbach Adventures decided May 15 that the risk that its clients or staff would get sick and be unable to get medical care was too great, said Lukas Furtenbach, the company’s managing director.

Hundreds of climbers and support staff reached Mount Everest’s base camp from late March through April, just as Covid-19 was surging in the region, eventually sweeping through Nepal and up to the camp at 17,500 feet.

Hundreds of climbers and support staff reached Mount Everest’s base camp from late March through April, just as Covid-19 was surging in the region, eventually sweeping through Nepal and up to the camp at 17,500 feet.

Photo: Furtenbach Adventures

Mr. Furtenbach, 43 years old, said he made the decision to call it off after several people in their camp, including Sherpa staff and an American climber, tested positive, despite their efforts to limit contact with other camps. All of them were taken by helicopters to clinics in Kathmandu. Most of the cases in the camps were mild, he said, although one person from a neighboring expedition camp needed to be put on oxygen and taken to a hospital in Kathmandu.

“The only logical decision for us was we have to cancel this expedition,” he said. “I was waiting for the government, for authorities, to call the season off already after the first cases in April. We were discussing every evening ‘when will they call the season off?’ But they didn’t.”

Lukas Furtenbach decided in May that the risk that his company’s clients or staff would get sick on Everest and be unable to get medical care was too great.

Lukas Furtenbach decided in May that the risk that his company’s clients or staff would get sick on Everest and be unable to get medical care was too great.

Photo: Furtenbach Adventures

Everest is a centerpiece of Nepal’s tourism industry, and the country’s cash-strapped economy needs the money it brings in. This season alone, the government received more than $4.1 million in royalties from climbing permits for Everest, among the highest since Nepal opened its mountain peaks for climbing in 1949.

In 2019, a record 1.2 million foreign tourists visited Nepal, more than 16% of them for trekking and mountaineering, according to government figures. That year, tourism brought in $724 million, or about 3% of Nepal’s gross domestic product.

The pandemic last year resulted in the loss of 20% of more than a million travel and tourism sector jobs in the country, which accounted for about 7% of the country’s total employment, according to the World Travel and Tourism Council.

Despite its importance to the economy, the climbing season has been canceled repeatedly in recent years, including in 2020 due to the pandemic. Climbing was halted in 2015 because of an earthquake and the year before that after an avalanche swept away 16 Sherpa and other local staff at the season’s start.

SHARE YOUR THOUGHTS

How do you think the pandemic will change the experience for climbers on Mount Everest? Join the conversation below.

The government decided to reopen Nepal for mountaineering last fall, long before the latest Covid-19 surge struck India and Nepal. Cases in India hit global highs in early May, topping 400,000 new daily cases. For several days in May, Nepal reported more than 9,000 cases and 200 deaths a day, the highest since the start of the pandemic. Public-health experts say the official numbers in both countries are likely far lower than the actual number of infections because of limited testing.

“Our mountain economy and tourism industry were on the verge of collapse due to the effects of the pandemic last year,” said Rudra Singh Tamang, the director general of the government’s Department of Tourism. “By opening for mountaineering this season alone, we believe we have saved the industry from collapse by infusing an estimated $85 million into the sector.”

Many people living in the Himalayas near Everest are dependent on the climbing season for their livelihoods, particularly those in the Sherpa and other ethnic communities who help the foreign climbers set up camps and carry equipment such as oxygen cylinders to the summit.

Several people in the Furtenbach Adventures camp, including Sherpa staff and an American climber, tested positive for Covid-19, despite their efforts to limit contact with other camps.

Several people in the Furtenbach Adventures camp, including Sherpa staff and an American climber, tested positive for Covid-19, despite their efforts to limit contact with other camps.

Photo: Furtenbach Adventures

Buddhi Bahadur Lama was among a dozen out of a team of 50 local Sherpa staff who tested positive for the virus in May. The 35-year-old farmer from a village in central Nepal said he had been eager to get back to the mountains after the cancellation of the climbing season last year deprived him of about $4,200 for three months of work. The money would have been enough to pay for a year’s education for his three children at private schools, rent for his room in Kathmandu and occasional get-togethers with his friends, he said.

“Those of us in the tourism sector were impacted badly. The government’s decision to allow climbing for this season was good for us,” he said.

The company that employed Mr. Lama, Tag Nepal Treks and Expedition Pvt. Ltd., had about 45 climbers this year from countries including the U.S., Mexico, Italy, Australia and the United Arab Emirates, according to Sagar Poudyal, one of its owners. The company evacuated about 10 or 11 Sherpa staff and four or five foreign climbers on helicopters to Kathmandu after they tested positive in antigen tests at Everest’s base, he said. Only a few of the evacuated Sherpa staff tested positive in more reliable PCR tests at a hospital in Kathmandu, he said.

Mr. Lama said he and another team member tested positive in the fourth week of May but stayed at the camp because they had only mild symptoms. “Other than the feelings of weakness while climbing up, I am fine,” he said in a phone conversation from the base camp. Only about 12 foreign climbers and 16 Sherpa staff from his team reached the summit this season, he said.

Covid-19 testing at the Everest base camp last month.

Covid-19 testing at the Everest base camp last month.

Photo: Furtenbach Adventures

Government tourism officials say they haven’t received reports from the expedition companies about confirmed Covid-19 cases among their team members and that authorities haven’t officially verified media reports of the outbreak at the base camp. Still, “we can’t say that there were no cases at all,” Mr. Tamang said.

He said that although the government had an economic imperative to continue with the climbing season, it didn’t overlook the health and safety of climbers and local staff, who were all required to test negative for the virus before leaving Kathmandu for base camp. Government officials deployed at the base camp were vaccinated, he said.

Mr. Tamang, however, acknowledged there was a flaw in the pandemic safety measures. Hundreds of porters carrying supplies to the base camp in backpacks or on yaks throughout the season weren’t tested for the virus. “We will carry this lesson to organize a coronavirus-free climbing season next year,” he said.

Mr. Furtenbach said he thinks the government was well intentioned in trying to avoid the economic damage of another canceled season, but he believes allowing climbing to continue amid the outbreak was the wrong decision. “You put people’s lives at risk and that’s not responsible, that’s not the right way for the government to handle such a situation,” he said.

Nepal’s government has acknowledged there was a flaw in the pandemic safety measures for Mount Everest. Hundreds of porters carrying supplies to the base camp throughout the season weren’t tested for the virus.

Nepal’s government has acknowledged there was a flaw in the pandemic safety measures for Mount Everest. Hundreds of porters carrying supplies to the base camp throughout the season weren’t tested for the virus.

Photo: Agence France-Presse/Getty Images

Write to Krishna Pokharel at krishna.pokharel@wsj.com