While a growing body of literature suggests a role for infections in Alzheimer's disease (AD), microbial contributions to AD remains a contentious topic, in part due to challenges in reconciling the positive evidence with studies reporting null findings. Here, we examine the evidence that argues against a role for infections in AD, while offering mechanistic hypotheses that may account for both the negative and positive findings, including dysregulated host immunity and gene-environment interactions of AD-associated genes.
Keywords: APOE; HSV‐1; amyloid beta; apolipoprotein E; infection; microglia; virus.
© 2026 The Author(s). Alzheimer's & Dementia published by Wiley Periodicals LLC on behalf of Alzheimer's Association.