“They are not in intensive care and they are in stable condition,” Jerker Jonsson, a Stockholm region infectuous disease specialist, told AFP.
“This is probably a case of Legionnaires disease,” he added.
The six were passengers on the Black Watch cruise ship, owned by Fred. Olsen Cruise Lines, which said the ship had been partially disinfected and tests of its water had been carried out to determine the source of the outbreak.
“Six passengers have been hospitalised in Stockholm,” company spokeswoman Wendy Hooper-Greenhill told AFP, adding that they were “suffering of pneumonia-like symptons and ship (crew) thought it would be better that they receive proper hospital treament.”
The ship had returned to sea carrying 756 passengers and crew members, mostly of British but also of Irish nationality, and was headed towards the British port of Dover, she said.
Before stopping in Stockholm the ship had passed through Saint Petersburg, the Estonian capital of Tallinn, the Finnish town of Kemi and Luleå in Sweden. It had also been scheduled to stop in Denmark and Norway, but the company had decided to cancel the last stops as a “precautionary measure”.
Hooper-Greenhill said once the passengers had disembarked the ship would be deep-cleaned.
Legionnaires’ disease – first discovered at an American Legion convention in the United States in 1976, where 29 people died – causes high fever, dry cough, lung congestion and subsequent pneumonia.
It is commonly spread through contaminated water sources, air conditioners and ventilators and is treated with antibiotics.