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article imageH5N1 avian flu virus linked to onset of Parkinson's disease

By Michael Krebs     Aug 11, 2009 in Science
The H5N1 avian flu virus - aka bird flu - does not usually infect humans, but at least one strain has shown that when it does it leaves us significantly more susceptible to the risk of developing Parkinson's disease.
Researchers are continuing to find disturbing links between relatively common viral infections and the onset of disruptive and deadly diseases. There have been studies that have shown viral links to skin cancer, concerns over the ties to mouth cancer, and associations between the H1N1 virus in mothers and autism in their unborn babies.
Now scientists have found that the H5N1 avian flu virus - also referred to as bird flu - is implicated with a significantly higher risk for developing Parkinson's disease.
"At least one strain of the H5N1 avian influenza virus leaves survivors at significantly increased risk for Parkinson's disease and possibly other neurological problems later in life, according to new research from St. Jude Children's Research Hospital," Science Daily reported on Tuesday.
The study was published in Proceedings of the National Academy of Sciences and centered on one strain of the H5N1, with infections being studied in mice. The virus was shown to have interacted with neurons, destroying roughly 17 percent of the same neurons that the Parkinson's and Alzheimer's family of diseases likewise destroys.
"This avian flu strain does not directly cause Parkinson's disease, but it does make you more susceptible," said Richard Smeyne, Ph.D., associate member in St. Jude Developmental Neurobiology, according to Science Daily. "Around age 40, people start to get a decline in brain cells. Most people die before they lose enough neurons to get Parkinson's. But we believe this H5N1 infection changes the curve. It makes the brain more sensitive to another hit, possibly involving other environmental toxins."
A key theory in the interactions of viruses and their long-term impact on human health was also supported in this research.
"This study also supports the theory that a hit-and-run mechanism is at work in Parkinson's disease," Science Daily reported. "The investigators believe the H5N1 infection sparks an immune response that persists long after the initial threat is gone, setting patients up for further devastating losses from a second hit, possibly from another infection, drug or environmental toxin. In this case, researchers believe the flu virus is the first hit that sets up development of Parkinson's at a later time."
While flu viruses most generally interact with the pulmonary system, it has been known for some time that inflammation caused by these infections have a direct impact on neurological function. This has been demonstrated most clearly in cases involving encephalitis. However, following the 1918 Spanish Flu pandemic, the connection between lung-based flu infections and neurological damage became more striking - as many of the Spanish Flu patients developed Parkinson's-like symptoms.
In the H5N1 study, researchers found that the inflammation within the brains of the surviving mice lasted for months - and it was a similar inflammation to that seen in an inherited version of Parkinson's disease.
"Researchers also found evidence that the avian flu infection led to over-production of a protein found in the brain cells of individuals with both Alzheimer's and Parkinson's diseases," Science Daily reported.
More about H5N1, Avian flu, Influenza, Parkinson, Neurological disorders
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