Olfactory Inflammation Stemming From Viruses May Hasten Onset of Alzheimer’s Disease

Past research has found that two common viruses – the varicella zoster virus, which causes chicken pox and shingles, and herpes simplex virus type 1, or HSV-1 – may play a role in the development of Alzheimer’s. Now, a new study finds that viral impacts on a portion of the body linked to smell – the olfactory system – may help hasten the onset of the disease.

Researchers from the University of Colorado Anschutz Medical Campus recently examined messenger RNA in the brain tissue of six Familial Alzheimer’s disease patients, compared with tissue from those without the disease, finding that those in the first group showed signs of viral infection in the olfactory bulbs, as well as inflammation in the olfactory tract, which carries information to the hippocampus. That’s a portion of the brain that deals with learning and memory and is impacted by Alzheimer’s. The team also found changes in the olfactory tract to myelin, a protective fatty layer around nerves that helps electrical impulses move more freely.


The findings, published in the journal Neurobiology of Aging, mean that viral infections and their impacts on the olfactory system may lead to the acceleration of Alzheimer’s. This builds on existing research linking scent with the disease.

Dr. Andrew Bubak, lead author and assistant research professor in neurology at the University of Colorado School of Medicine, says, “We know that one of the early signs of Alzheimer’s disease is losing the sense of smell.”

Meanwhile, Dr. Diego Restrepo, co-senior author and professor of cell and developmental biology at the CU School of Medicine, says, “Our hypothesis is that some viruses accelerate Alzheimer’s disease. Does the loss of smell specifically accelerate Alzheimer’s? That’s the question.”


The team believes that inflammation and amyloid deposits in the olfactory system may decrease signaling with the hippocampus, leading to a lack of sensory input, which causes the hippocampus to degenerate.

Going forward, the researchers hope to learn more about viral impacts on neurodegeneration and the olfactory system-hippocampus connection.

To read more on the study, click here.

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