MAPT and viral infectious disease: Another in-vitro model on human-brain organoids infected with the COVID-19 virus showed the aberrant phosphorylation of the tau protein, p tau 231, resulting in neuronal cell death after infection with SARS-CoV-2.A variety of body stresses, including viral infection, can trigger pathological tau protein, which can possibly spread to healthier naive cells through synapses, resulting in functional and structural changes in the peripheral and autonomic nervous system, as discussed above.