Each year, millions of people sustain a traumatic brain injury (TBI), often resulting in serious, long-term consequences. Research indicates that even one head injury is linked to a higher risk of developing dementia, with the risk increasing further after two or more. A recent study found that TBIs can reactivate dormant herpes simplex virus type 1 (HSV-1), driving neuroinflammation and contributing to the development of Alzheimer’s.
Researchers created a three-dimensional model of the human brain. Then, they subjected HSV-1-infected and non-infected brain tissue to multiple blows, emulating TBIs and their ensuing pro-inflammatory effects.
They found that repeated mild blows to HSV-1-infected tissues reactivated the virus, triggering inflammatory processes in the brain and driving the buildup of amyloid-beta and phosphorylated tau—proteins linked to brain damage and memory loss. These harmful effects worsened with additional injuries but didn’t occur in uninfected tissue.
These findings demonstrate that viral reactivation in the brain may contribute to the development of Alzheimer’s. HSV-1 is the virus responsible for causing cold sores and genital herpes. It infects approximately 80% of people by age 60 and is commonly found in the brains of older adults. In people with the APOE4 gene, HSV-1 markedly increases the risk of Alzheimer’s.