TORONTO - Renovating may be all the rage when its comes to older homes, but in some cases there could be danger lurking behind those long-standing walls.

That was the case in Quebec, where more than a dozen people became ill with a pneumonia-like infection after the exterior brick of a century-old house was removed as part of a renovation.

The outbreak, which occurred in May, was reported Thursday in the U.S. Centers for Disease Control and Prevention's weekly morbidity and mortality report.

Fourteen people — including workers, residents of the house and neighbours —developed symptoms of histoplasmosis, a fungal disease carried in the droppings of bats and birds. Two of the workers were admitted to hospital and the regional public health department was called in to deal with the outbreak.

"We had a declaration from a family doctor who had seen two cases, and he was astute enough to realize that something was probably going on at (their) work," said Dr. Jean-Luc Grenier, a medical consultant at the Laurentians Public Health Department and a co-author of the CDC report.

The home was owned by a married couple who lived on the ground floor of the two-storey house and rented the upper floor to two tenants. The couple had decided to renovate because the exterior brick walls were cracked and in danger of falling.

"There were probably some bats that were able to live there in-between the bricks and the (interior) walls," Grenier said of the home, located in Saint-Eustache, Que., northwest of Montreal.

Over the years, bat droppings containing histoplasmosis spores would have built up inside the walls, he said. As the bricks were pulled down, clouds of dust carrying the dried spores would have become airborne and easily breathed in by anyone nearby.

Grenier said an investigation determined 30 people had been exposed to the spore-laden dust. Of those, 14 got sick with symptoms of histoplasmosis infection, which include high fever, coughing, chest pain and shortness of breath.

Those affected included six masonry workers, the two homeowners, a visitor to the house, two neighbours whose bedroom faced the demolition site, and three debris sorters. The two renters within the home did not get sick.

The debris sorters weren't located in Saint-Eustache, but in the Lanaudiere region many kilometres away, and were unwittingly exposed to histoplasmosis spores.

"Those bricks, I don't know why, but they decided to recycle them," Grenier said. "So before knowing there was an outbreak, the bricks were brought in a container to another region far away." There, two workers cleaned the bricks so they could be reused.

"So they were brushing them to take off the dirt. Those two were very sick also because they were exposed directly. They didn't wear any masks."

To remove the health risk, all the bricks taken for recycling were buried, while heavy rains over a few days at the renovation site would have washed away any lingering spores, Grenier said.

All of those sickened recovered and none needed treatment with antifungal medication. Typically, the body's immune system is able to get rid of the infection, although that isn't always the case: people with compromised immune function, such as those being treated for HIV or some cancers, usually need drug treatment.

In rare cases, histoplasmosis can be fatal, even with antifungal therapy.

"It depends on the dose you get into your lungs and your immune system," Grenier said. "If, for instance, a neighbour had been an old man with immunosuppression, he could get the disease and die."

While the fungus is widely present in soil, cases of histoplasmosis infection are rare in Canada and usually involve construction work that stirs up clouds of dried-up aerosolized spores that people end up inhaling.

That's why workers and their employers need to strictly adhere to labour regulations requiring that protective masks or respirators be worn while doing jobs that produce potentially harmful, breathable forms of dust, he said.

In this case, the workers had been given masks but didn't wear them continuously because the weather was hot.

"The principal message is for workers, because it's workers who probably (have) the most potential to be exposed."