How is viral meningitis diagnosed?

Several ways: There are changes in the spinal fluid in cells, protein and glucose. There is a difference sometimes in the clinical presentation. Sometimes you can isolate the virus or detect its presence by antigen or antibody testing.

Dr Ali and another doctor agreed

Aseptic: Meningitis is an inflammation of the outer coating of the brain. A spinal tap will show inflammatory cells in spinal fluid. Bacteria will be seen and cultured if present. If nothing grows it is considered aseptic. This usually means that a virus is the cause. Special tests and cultures may or may not identify the virus. Viruses may infect the brain itself causing encephalitis.