The 45-year-old man is being treated in an Edmonton hospital after returning from Valemount, B.C.
Friends say the man is an avid snowmobiler who contracted the disease in a hot tub.
The disease is a form of pneumonia and its bacteria are found in water sources. It is not spread person to person. Symptoms include fever, chills and coughing.
Dr. William Osei (OH-SAY), medical health officer for Northern Health Authority, Northern Interior Health Service Delivery Area, said they are trying to determine where the person contracted the disease.
"This is the top priority ... We are looking at the prevention and control side and Alberta is looking at treating this person," he said.
He said they just found out about it on Sunday from Alberta Health Services. The man is not able to speak because he is intubated, so they are getting their information from his relatives, Osei added.
Health officials in B.C. are also checking hotels and motels in the Valemount area.
"We talked to all facilities and no one has reported any malfunctions or breakdowns in the systems they have," Osei said.
The environmental officer for Northern Interior Health Services was to go to Valemount on Tuesday to talk to owners of hotels, motels and other accommodations to "educate them" and take some samples from vents, swimming pools, saunas and hot tubs.
Osei says those samples will be sent to Vancouver for testing, and results may be back by Thursday or Friday.
"We are asking the public not to panic because this is a rare condition and it doesn't spread from person to person, you inhale it or aspirate it," he said.
"We are appealing of owners in the area of large air conditioning and hot-water systems, as well as private saunas and hot tubs who may be situated in cabins away from the town to call (us) so we can advise them of proper disinfection and maintenance of their system."
The laboratory in Edmonton has tentatively confirmed the bacteria the man has is Legionella pneumophila, and the sample is being sent to National Microbiology Laboratory in Winnipeg for further tests, said Osei.
The incubation period for legionnaires' disease is generally less than a week, but it can take from two to 10 days for symptoms to show, Osei said, adding the hospital in Valemount has had no cases recently.
There has been no cases of legionnaires' disease in the area since Osei began working there four years ago. He said on average, there are between five and seven cases each year in B.C.
Nine people were hospitalized in Alberta last year with the disease; one died.
(The Canadian Press, CKNW)