This review examines whether germs like bacteria, fungi, and viruses might play a role in causing Alzheimer’s disease. Scientists have found that certain bacteria from the mouth and gut, fungal infections, and cold sores (herpes viruses) appear more frequently in Alzheimer’s patients and may trigger the brain changes that damage memory and thinking. While the evidence is promising, researchers still need to determine whether these infections actually cause Alzheimer’s or simply make it worse once it develops.