Michael J. Fox, three co-workers at 70s TV show, all got Parkinson's

Parkinson's disease may be caused by a virus.

Canadian-born actor Michael J. Fox, while working on a CBC sitcom as a teenager, contracted a virus that some researchers say may have caused him to later develop Parkinson's disease.

Fox worked on show Leo and Me in Vancouver in 1977.

Researchers studying the degenerative disease theorize that exposure to viruses or environmental toxins can trigger its onset years later.

According to Dr. Donald Calne, director of the Neurodegenerative Disorders Centre at the University of B.C. Hospital, Parkinson's can develop in clusters of people, such as teachers or workers who live close to each other.

Fox is one of four Leo and Me workers who have been diagnosed with Parkinson's, which leads to muscle rigidity, tremors and involuntary movements.

Calne is treating two people who worked with Fox on the short-lived Canadian sitcom.

Japanese researchers have established that a virulent form of the flu, caused by a virus, can make its way into the same part of the brain that Parkinson's attacks.

Fox left the popular TV series Spin City to raise money for Parkinson's research.