The Sudbury and District Health Unit is cautioning people to visit their physician if they develop any respiratory issues after having spent time in damp, moist areas.

Their advice comes after a cluster of between five to seven children from the western portion of Manitoulin Island were infected with blastomycosis, a rare fungal infection.

Blastomycosis infects the lungs after fungal spores are inhaled, usually when contaminated soil is disturbed.

The infection produces symptoms —  difficulty breathing and coughing — so similar to pneumonia that the infection many times is misdiagnosed, said Holly Browne, a manager with the health unit's environmental health division.

"It's a fairly rare infection," Browne said. "We're seeing an increase now, and we're not sure why."

The people reporting the infections are in an area that has prime conditions — damp and moist woodlands — for the fungus to grow.

"It's usually in moist, acidic soil," Browne said. "Anywhere there's decaying wood, decaying leaves, which would make the soil more prone to growing fungus."

"We're not 100 percent sure, but our understanding is it's a white fungus. When you disturb the soil whether through gardening, construction,even playing in it the spores go airborne and it can be inhaled."

Browne said about 50 per cent of people who are infected end up showing symptoms. Of those who do show signs, it's usually because they are already compromised healthwise or have restricted ability to fight off infections.

The kids infected live in an area serviced by First Nations-Inuit Health Branch, who have been collecting information. As of yet, there is no clear indication where the people encountered the fungus.

"We don't have an exact source," Browne said. "But based on the fact the individuals are all from the same community, we believe they were exposed to a common source."

Browne said she understands that the majority of those infected have been discharged from hospital and returned back to their community.

She added that she's heard stories of dogs being infected with the fungus, but that information is handled by veternarians, not the health unit. 

With files from CBC's Olivia Stefanovich