The role of viruses in neurodegenerative and neurobehavioral diseases.

Neurodegenerative and neurobehavioral diseases may be caused by chronic and neuropathic viral infections and may result in a loss of neurons and axons in the central nervous system that increases with age. To date, there is evidence of systemic viral infections that occur with some neurodegenerative conditions such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, multiple sclerosis, autism spectrum disorders, and HIV-associated neurocognitive disorders. With increasing lifespan, the incidence of neurodegenerative diseases increases consistently. Neurodegenerative diseases affect approximately 37 million people worldwide and are an important cause of mortality. In addition to established non-viral-induced reasons for neurodegenerative diseases, neuropathic infections and viruses associated with neurodegenerative diseases have been proposed. Neuronal degeneration can be either directly or indirectly affected by viral infection. Viruses that attack the human immune system can also affect the nervous system and interfere with classical pathways of neurodegenerative diseases. Viruses can enter the central nervous system, but the exact mechanism cannot be understood well. Various studies have supported viral- and non-viral-mediated neurodegeneration at the cellular, molecular, genomic and proteomic levels. The main focus of this review is to illustrate the association between viral infections and both neurodegenerative and neurobehavioral diseases, so that the possible mechanism and pathway of neurodegenerative diseases can be better explained. This information will strengthen new concepts and ideas for neurodegenerative and neurobehavioral disease treatment.