Viremic attack explains the dual-hit theory of Parkinson's disease.

The dual-hit theory of Parkinson's disease proposes that an airborne pathogen attacks both the olfactory and enteric nervous systems to initiate the Lewy pathology, gradually leading to devastating neurodegenerative processes within the brain. Based on published literatures, this article proposes a hypothesis that viruses with viremic potential can simultaneously attack both of these nervous systems via viremia due to the lack of a blood-nerve barrier in these tissues, thereby explaining the dual-hit theory. Understanding the precise mechanisms underlying the neuropathology will facilitate development of better prophylactic and early intervention strategies against Parkinson's disease.