Like a relay, infections with the microbes initiate the formation of alpha-synuclein “prions” which keep seeding, spreading and conforming (normal alpha-synuclein proteins to pathological prion-like alpha-synuclein proteins), inducing neuroinflammation and subsequent neurodegeneration, and causing damage and neuronal loss to dopaminergic neurons in the substantia nigra in sporadic PD. This evidence concerns the gene SNCA and infection.