A few days ago I read an article on Nature Scientific Reports about Fungi in the brain of Alzheimer's Disease patients. The article didn't go as far as proposing a causal relationship. But if a relationship existed this could be a dramatic discovery. It would have the potential to revolutionize the life of dozens of millions of people around the world who suffer Alzheimer's disease.
It reminds me of the discovery that ulcers are caused by bacteria. The conventional medical knowledge until the 1980s was that ulcers were caused by excessive acid. As it turned out, Marshall and Warren found out the real cause was the H.pylori bacteria.
Another interesting bit from this article is that the research comes from the Universidad Autónoma de Madrid. I haven't seen a lot of research originally from Spain being widely discussed in publications like the Economist or in Hacker News, where they raised criticisms to the methodology in the paper. In any case, I'm hoping that we will see follow up studies.