According to the hospital, his condition is serious but stable.
The case represents the first on Swedish soil involving someone suffering from such grave symptoms due to infection with the AH1N1 flu virus.
“So far this is the most serious case in Sweden of which I am aware in the current H1N1-flu epidemic. It’s very serious,” said Christer Liedgren, the hospital’s chief doctor, to the Svenska Dagbladet (SvD) newspaper.
The man is believed to have contracted the disease while on vacation in southern Europe.
He became ill five days ago and was prescribed the anti-flu drug Tamiflu.
According to the hospital, the 22-year-old is no long contagious, but has developed pneumonia as a result of the flu infection.
“It’s the complications which have made the situation so serious. Right now things are under control, but we’re following developments and the patient is under constant observation in intensive care,” Liedgren told SvD.