The original realization of post-encephalitic Parkinson’s disease was based on typical viral induced glial nodules in the substantia nigra of brains of people dying acutely during the pandemic, with survivors developing post-encephalitic tau positive neurofibrillary tangles (NFT) that are also present in AD, in traumatic dementia pugilistica, and in subacute persistent measles infections (subacute sclerosing pan-encephalitis). The gene discussed is MAPT; the disease is Alzheimer disease.