Parkinson's disease occurs when brain cells that produce an important hormone called dopamine begin to die off or become impaired. As dopamine levels decrease, people develop movement symptoms like shaking or stiffness, as well as problems maintaining balance and coordination.

Parkinson's disease is a neurogenerative disease that affects more than 1 million people in the U.S. While some cases are caused by genetics, the cause is unknown in most.

Researchers have detected a common, previously considered harmless virus, Human Pegivirus (HPgV), in the brains of Parkinson’s patients, raising new questions about its possible role in triggering the neurodegenerative disease.