(CNN) -- An international youth camp in western Norway is being shut down after swine flu broke out among the teenagers, the organizers, 4H Norway, announced Saturday.
Of the 1,700 participants, 37 have developed symptoms of swine flu and are now in isolation in the town of Gloppen. No one is seriously ill, however, and no one has been hospitalized, a source in the Norwegian Directorate of Health told CNN.
All of those affected had traveled to the youth camp in the same bus.
"People are mostly sad that they have to go home now since they have been preparing for this camp for so long," Astrid Solberg, secretary-general of 4H, told CNN.
Children from 15 countries are at the camp, which was supposed to end next Wednesday.
On Friday, a Norwegian girl at the camp was confirmed to have swine flu, 4H said. She developed high fever Thursday and was immediately attended to by doctors at the camp, 4H said.
The girl previously had been with her mother in Cyprus, where she probably contracted the disease, the Norwegian Health Directorate told CNN.
Another 20 people developed symptoms of swine flu Friday.
By Saturday morning, 37 youths were suspected to have caught the disease.
Because of the swine flu outbreak, the organizers, together with Norwegian health authorities, have now decided to gradually shut down the camp, 4H said.
"It will take a while because we are so many here, but we are sending people home as soon as possible," Solberg told CNN. "But there is no panic and no anxiety. People are mostly just sad."
While organizers are planning the departure of the participants, everyone at the camp is being urged to maintain good hand hygiene, according to a statement posted on the 4H Web site.
In Norway, there are around 200 confirmed cases of swine flu, with three people hospitalized.
The virus has been confirmed in 18 of Norway's 19 counties, according to the Norwegian Health Directorate.