Health: What are these viruses that would cause diseases such as Alzheimer’s and Parkinson’s?

New epidemiological evidence shows that Alzheimer’s and Parkinson’s diseases could be caused by viral infections

For several years, scientists have been talking about the role of microbial or viral infections in the occurrence, even years later, of neurodegenerative diseases such as amyotrophic lateral sclerosis, Alzheimer’s disease, vascular dementia, multiple sclerosis, Parkinson’s disease and generalized dementia.

It is by digging into the data of two biobanks, The FinnGen in Finland and the UKB in the United Kingdom, that American data scientists have tried to go further and provide new evidence of this link between viruses. and neurodegenerative diseases.

The role of herpes confirmed

Kristin S. Levine’s team was thus able to rely on data from hundreds of thousands of patients and demonstrate 45 virus-disease associations in the first biobank which could be replicated 22 times with the second biobank.

Long evoked, the link between the varicella virus or shingles has been confirmed in the manifestation of more than one neurodegenerative disease.

But the greatest association of effect was seen between exposure to viral encephalitis (inflammation of the brain during an infection) and Alzheimer’s disease. Influenza with pneumonia was significantly associated with five of the six neurodegenerative diseases studied. The study thus confirmed the link revealed by a recent Danish study between influenza and Parkinson’s disease.

Scientists have also reproduced the association between the Epstein-Barr virus and multiple sclerosis.

Herpes also affects the onset of Alzheimer’s disease, genital warts on dementia, hepatitis and Alzheimer’s disease.

How do these viruses attack the brain?

According to this study published in the journal Neuron, these viruses increase the risk of neurodegenerative disease by reducing “cognitive reserve through brain inflammation”. “All of these viruses were linked to a high risk of manifestation of neurodegenerative disease. Approximately 81% of the viruses were found to be neurotrophic, indicating that they can attack the central nervous system via peripheral nerves or by crossing the blood-brain barrier “.

Many vaccines exist against these viral infections, and for the authors of the study, like the anti-Covid vaccine, if they do not prevent the disease, they would avoid serious forms and their consequences.

This study calls out and should trigger in-depth research on the subject. Its main limitation, as Professor François Balloux points out, is “that around 100% of the population has been infected several times with the flu and around 95% with the Epstein-Barr virus (…). Everything it may be a bit more complicated than this article suggests…”

Viral infections are not nice, but since ~100% of the population has been infected with influenza multiple times, and ~95% with EBV, I suspect this may all be a bit more complicated than this paper suggests …

— Prof Francois Balloux (@BallouxFrancois) January 20, 2023

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