Washington: After a week of sore throat and body pain, severity of your flu may wear off. But a new study has claimed that such viral infections could have lasting and unseen effects on your brain.
Researchers have found that viruses such as influenza and herpes may leave brain cells vulnerable to degeneration later in life, and increase the risk of developing diseases such as Alzheimer`s and Parkinson`s.
That`s because these the viruses can enter the brain and trigger an immune response -- inflammation -- which can damage brain cells, said Dr Ole Isacson, a professor of neurology at Harvard Medical School, who led the study.
"Viruses and other sources of inflammation may be initiating factors in some of the most common neurological diseases," Dr Isacson was quoted as saying by LiveScience.
It`s unlikely one bout of the flu will cause significant damage. But over a lifetime, injuries to cells accumulate, and along with environmental stresses, this can kill cells and the development of brain diseases, Isacson said.
Variations in the number of infections we get may be the difference between a person developing Parkinson`s disease at age 65 or at age 95, he said.
The researchers said it`s possible that toning down the inflammation that occurs shortly after viral infection could reduce cell damage and the risk of subsequent brain disease.
In the research, published in the journal Science Translational Medicine, they pointed to a 2011 study of 135,000 people which had found that those who took ibuprofen (a medication that can reduce inflammation) were 30 per cent less likely to develop Parkinson`s over a six year period compared to those who did not take the medication.
One of the earliest evidence for the virus-brain disease link comes from the 1918 influenza pandemic, they said. In a more rigorous test of the link, a 2009 study showed that mice injected with the H5N1 flu virus developed infections in cells in a brain region known to be significantly impacted by Parkinson`s disease, Isacson said.
Research has also shown that infection with certain herpes viruses can increase the risk of Alzheimer`s disease. And very rarely, encephalitis, or brain inflammation caused by viruses, can lead directly to an acute, but transient, form of Parkinson`s disease.
But more often, viral infections in our brain are silent, Isacson said. We don`t see the full impact of these infections until brain degeneration is substantial, he said.
Several weeks after infection, inflammatory molecules known as cytokines reach a peak concentration, Isacson said. It`s this "cytokine storm" that Isacson and his colleagues suspect is responsible for the brain cell damage associated with viral infections.
If researchers could find a way to block this peak from occurring, they might reduce the risk of certain neurological diseases, Isacson said.
In addition, researchers could also try to identify viruses that cause particularly severe cytokine storms, to better understand which infections pose the greatest risk to the brain, Isacson said.
However, the researchers said more research is needed to understand what, if any, effect the immune system has on brain diseases.