Bird flu infection in brain may be tied to Parkinson's disease

Avian flu can travel into the brains of mice, killing cells and causing symptoms that look like Parkinson's disease, a study has shown.

The disease, caused by the H5N1 virus, traveled up the vagus nerve that links the stomach to the brainstem, according to a report in the Proceedings of the National Academy of Sciences. The infection caused cell death in brain areas that make dopamine, which is involved in body movement. Parkinson's symptoms include slowness of movement, rigidity and tremor.

The finding reinforces the need to monitor both swine flu and seasonal flu in people because either can cause neurological symptoms including personality changes, loss of concentration, brain swelling and death in a small number of cases, according to a report from the U.S. Centers for Disease Control and Prevention in Atlanta.

"The idea that flu viruses can cause neurological disease is underappreciated," said Richard Smeyne, an author of the study and a neurologist at St. Jude Children's Hospital in Memphis, Tenn. "We need to watch for this in other flus."

The 1918 pandemic flu may have infected the brain in some people, causing von Economo's encephalopathy, or sleeping sickness, Smeyne said.

"This is an indication that an infection with influenza is more than an upper respiratory disease," said Christopher Woolverton, an infectious disease microbiologist and director of Kent State University's center for Public Health Preparedness. "If this research is borne out, we're going to have to pay a lot more attention to flu as an infectious disease and figure out more completely the effects on the body."

Most of the time, the flu virus doesn't get into the brain, Smeyne said. When it does, it can cause a condition called encephalitis, a group of neurological symptoms that might include a stiff neck, vomiting, confusion, drowsiness, memory loss and coma. Extreme cases can cause death.

About 5 percent of childhood encephalitis arises from seasonal influenza, according to the CDC report.

One way to confirm the mouse findings in humans would be to follow H5N1 survivors to see if they have abnormally high rates of Parkinson's disease or other neurological disorders, Smeyne said. Avian flu, which killed 261 of 424 people known to have been infected, spread to Europe and the Middle East from Asia in late 2005.