Once found only in Ontario, Lyme-carrying ticks are now found in almost all the provinces. As they continue to spread, medical professionals are increasingly concerned about Canadians contracting the disease.

"The distribution has changed," infectious disease specialist Dr. Neil Rau told CTV's Canada AM on Monday.

Rau said the risk of contracting Lyme disease used to be limited to Point Pelee and Fort Erie, near the U.S. border in southern Ontario. Now, the organisms that cause the disease can be found almost everywhere along the border, he said.

Lyme-carrying ticks have been found in southern Quebec, Manitoba, southern New Brunswick, southwest Nova Scotia, Saskatchewan, Alberta, and B.C.

"The distribution of the tick and the distribution of the organism is definitely spreading," Rau said.

Climate change is often seen as a reason for the tick migration from the U.S., Rau said.

In order to contract Lyme disease, a person would have to be bitten by a tick that is carrying the disease.

"It needs outdoor exposure. You're not going to get this walking around in the cities that are in those geographic areas," he said. Ticks are found in river valleys, forests, tall grass and other natural environments.

Canada reported 500 cases of Lyme disease in 2014, but expects 10,000 Canadians will be infected annually by 2020.

Rau warned that many people may not realize they have contracted Lyme disease immediately.

Toyah Israelstam suffered from the disease for several years, and said she thought it was something minor at first.

"I started developing symptoms slowly over time," Israelstam said. At different times, she suffered hair loss, rash and sleep deprivation, but doctors weren't sure what was wrong with her.

It took two years for doctors to reach a diagnosis. She decided to see a specialist south of the border on a doctor's advice.

Rau said both Canadian and American officials diagnose the disease based on a series of blood tests, but some people don't immediately test positive. Patients are often advised to go to private labs in the U.S. if they can't be diagnosed in Canada.

If the disease is caught early on, patients are prescribed a course of antibiotics and can recover quickly. If it takes several years to diagnose, some of the disease's effects can be permanent, including neurological or cardiac damage.

Israelstam said she had to undergo several years of antibiotic and naturopathic treatments for what she feared would be permanent damage.

"Sometimes symptoms seem like they might be irreversible, but keep on treating. I never gave up and I'm getting better," she said.

"I never thought I'd come this far, ever, because I was so sick for so many years."

Symptoms of Lyme disease