infectious disease encephalitis infectious encephalitis UMLS:C0596773 ICD9:049.8 GARD:0025151 MEDGEN:108917 MESH:D000069544 MONDO:0020067 NCIT:C79550 SCTID:312215006 An acute infectious process that affects the brain tissue. It is usually caused by viruses and less often by bacteria, parasites, and fungi. encephalitis infection ICD9:323.4 central nervous system infectious disorder