Researchers have linked chronic intestinal infections caused by cytomegalovirus (HCMV) to a unique subtype of Alzheimer’s disease. The virus may travel from the gut to the brain via the vagus nerve, altering immune responses and contributing to hallmark Alzheimer’s changes like amyloid plaques and tau tangles. While HCMV infection is common and typically harmless, this study found that it may cause chronic brain inflammation in certain individuals.