Thanks for your link jeffreyn - it is interesting.

The idea that infectious agents may be significant in some cases of sporadic AD has been round for a while. There is a free-access discussion of this here Can Infections Cause Alzheimer's Disease? | Epidemiologic Reviews | Oxford Academic.

Dr Balin has focused on the possible role of Chlamydia pneumoniae infection in AD.

Some independent investigators have tried and failed to replicate some of his reported findings about this (see article above). It is curious that Dr Balin chose not to mention this in his opinion piece. I can only speculate about the reasons for this omission...

Overall, I would put this concept into the "interesting but unproven" basket - as the authors of the discussion above point out, a lot more work is needed before we know what is going on.