Central Nervous System (CNS) infections are caused by bacteria, viruses, fungi, helminths, with several clinical aspects. Studies in the literature generally focus on a single patient type, and no experiences have been reported in which immunosuppressed and immunocompetent adult and pediatric patients were simultaneously examined. Our study will include all possible patient types (immunocompetent adults, immunocompetent pediatric patients, and subjects immunosuppressed by co-softness), to try to more precisely define the clinical and population characteristics of patients who have had an episode of CNS viral infection. These indications may be useful in the future to more specifically guide diagnostic investigations on patients considered at risk.