EBV-associated CNS Infection in an Immunocompetent Adult: A Case Report and Literature ReviewGwyn Srifuengfung, MD1, Pichatorn Suppakitjanusant, MD1, Nattanicha Chaisrimaneepan, MD21Department of Neurology, Texas Tech University Health Sciences Center, Lubbock, TX, USA2Department of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, USACorresponding author: Nattanicha Chaisrimaneepan, MDDepartment of Internal Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, USA3601 4th St, Lubbock, TX 79430Email: [email protected]: All the authors declare no conflict of interest.Verbal and written consent was obtained from the patient to publish his case.AbstractEpstein-Barr virus (EBV) infections typically manifest with respiratory symptoms, lymphadenopathy, and, rarely, central nervous system (CNS) involvement. We report an uncommon case of an immunocompetent 18-year-old male with altered mental status due to EBV-associated CNS infection. The patient, with a recent history of infectious mononucleosis, presented with fever and meningeal irritation signs. Initial investigations revealed leukocytosis, atypical lymphocytes, and positive heterophile antibodies, but a head CT scan was normal. Empirical treatment for bacterial meningitis was initiated. Results of further assessments, including a positive EBV serology, a consistent cerebrospinal fluid analysis and positive EBV DNA in the CSF led to the diagnosis of EBV-associated CNS infection-more specifically meningoencephalitis. Neuroimaging, including MRI, showed no abnormalities. The patient improved with supportive care and a four-day course of acyclovir. We discussed the challenges in diagnosing EBV-associated CNS infection, emphasizing the role of CSF PCR in confirming the diagnosis. The importance of ruling out other infections is highlighted, and the heterogeneity in the mechanism of infection is explored. The case underscores the significance of recognizing an isolated, active EBV infection in young adults with altered mental status, especially when more common causes have been excluded.Keywords: Epstein-Barr virus, CNS infection, aseptic meningitis, altered mental status, CSF PCR, viral encephalitis.