Severe Central Nervous System Co-infection With Streptococcus pneumoniae and Varicella-Zoster Virus Presenting as Meningoencephalitis.

Prompt identification of bacterial and viral central nervous system (CNS) infections is crucial; however, co-infection remains rare and diagnostically challenging. We report the case of a 61-year-old woman who presented with altered mental status and was initially suspected of having a stroke but was later diagnosed with severe sepsis and meningitis. Cerebrospinal fluid (CSF) analysis revealed elevated protein levels, and nucleic acid amplification testing (NAAT) identified concurrent Streptococcus pneumoniae and varicella-zoster virus (VZV) infection. Blood cultures subsequently confirmed S. pneumoniae bacteremia. Furthermore, the hospital course was complicated by metabolic encephalopathy, non-ST-segment elevation myocardial infarction (NSTEMI), and acute kidney injury (AKI). This case highlights the importance of maintaining a broad differential diagnosis and considering mixed CNS infections in atypical presentations while emphasizing the value of molecular testing. Early recognition and targeted therapy are essential for improving neurological outcomes in critically ill patients.