KATHMANDU, Nepal — A Norwegian climber became the first to be tested for COVID-19 in the Mount Everest base camp and was flown by helicopter to Kathmandu, where he was hospitalized.

Erlend Ness told The Associated Press in a message Friday that he tested positive on April 15. He said another test on Thursday was negative and he was now staying with a local family in Nepal.

Mountain guide Lukas Furtenbach, warned that if safety measures are not taken, the virus could spread among the hundreds of other climbers, guides and helpers who are now camped on the base of Everest.

Furtenbach, leading a team of 18 climbers to Mount Everest and its sister peak Mount Lhotse, said there could be more than just one case on the mountain as the Norwegian had lived with several others for weeks.

Any outbreak could prematurely end the climbing season, just ahead of a window of good weather in May, he said.