A 'harmless' virus carried by half of all adults could increase the risk of Alzheimer's, according to shocking new research.
Cytomegalovirus (CMV), which causes a cold-like illness, can be spread in the same way as other viruses from one person to another through bodily fluids such as blood, saliva, and urine.
But infection is present in up to 45 percent of Alzheimer's cases, American scientists have claimed.
Some people exposed to this virus can develop a chronic intestinal infection, allowing the virus to enter the bloodstream and travel to the brain.
There, microglia – the brain's immune cells – recognize it, contributing to the biological changes associated with Alzheimer's, the researchers say.
Scientists, who have described the discovery as 'exciting', hope that this research could pave the way to confirm whether common antiviral drugs used to treat CMV can help prevent this form of the memory-damaging disease.
However, they warned that mere contact with the virus — which happens to almost everyone — should not cause concern.
The infection appears to be linked to Alzheimer's only when it is found in the brain.
So far, no single disease has been consistently linked to this disease.
Dr. Ben Readhead, co-author of the study and associate professor of neurodegenerative diseases at Arizona State University, said:
"We think we have discovered a unique biological subtype of Alzheimer's that may affect 25 to 45 percent of people with the disease."
This subspecies, he added, GazetaExpress reports It contains a buildup of amyloid and tau proteins in the brain — a hallmark of Alzheimer's — as well as a 'particular profile of the virus [CMV], antibodies and immune cells in the brain.'
In the study, scientists examined cerebrospinal fluid to track how CMV antibodies move in the body.
They found CMV within the vagus nerve, which sends signals between the brain, heart and digestive system, and suggested that this was how the virus travels to the brain.
Tests on human brain cells then showed that the virus increased the production of amyloid and tau proteins and contributed to the degeneration and death of neurons.
Writing in the journal Alzheimer's and Dementia, the researchers said the study illustrates the impact that infections can have on brain health and neurodegeneration in general.
But they added that further independent studies are needed to test their findings and hypotheses.
Dr. Eric Reiman, executive director of the Banner Alzheimer's Institute and lead author of the study, also said: "We are excited about the opportunity for researchers to test our findings in ways that make a difference in the study, treatment and prevention of Alzheimer's."
A recent analysis by the Alzheimer's Society estimates that the total annual cost of dementia in the UK is £42 billion, with families bearing the brunt.
An ageing population means these costs – which include the lost income of unpaid carers – are expected to rise to £90 billion in the next 15 years.
Around 944,000 people in the UK are thought to be living with dementia, while the figure in the US stands at around 7 million.
Alzheimer's affects about six in ten people with dementia.
It is thought to be caused by a buildup of amyloid and tau proteins in the brain, which form plaques and tangles that make it harder for the brain to function.
Over time, the brain fails to cope with this damage and symptoms of dementia appear.
Problems with memory, thinking, reasoning, and language are common early symptoms of the condition, which worsen over time.
The increase in dementia cases in the coming years makes an inexpensive diagnostic tool necessary to meet this challenge.
Analysis by Alzheimer's Research UK found that 74,261 people died from dementia in 2022, compared with 69,178 the year before, making it the biggest killer in the country. /GazetaExpress/
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