The pathogenesis of Alzheimer’s disease （AD） remains elusive. Pathogen infection has long been proposed as a causative factor of AD. By directly infecting the central nervous system or indirectly affecting other systems， pathogens may activate the immune system， promote amyloid formation， and impair neuronal function， leading to the development of AD. The purpose of this article is to elucidate the pathological connection between infection and AD and to review the available evidence.