ACE2 and viral encephalitis: ACE2, brain, CNS, COVID-19, cytokine storm, encephalitis, headache, encephalopathy, viral infection, inflammation, meta-analysis, MRI, neurodegeneration, neuroinflammation, neuroinvasion, neurological, neurological manifestations, neurological symptoms, neurology, neurotropism, olfactory bulb, olfactory epithelium, Parkinson's disease, risk factors, SARS, SARS-CoV-2, stroke, systematic review (n = 28)