In PD, infections with pathogens such as influenza A virus, SARS-CoV-2, West Nile virus, and gut bacteria (e.g., Desulfovibrio bacteria) can trigger an anti-pathogen accumulation of alpha-synuclein and alpha-synuclein pathology (misfolding, aggregation, etc.), and evoke “prion” formation that conforms normal alpha-synuclein proteins to pathological prion-like alpha-synuclein proteins (5, 23, 92, 109, 111, 133, 134). Here, SNCA is linked to Parkinson disease.