Published data suggest that encephalitis is one of the most fatal neurologic manifestations of coronavirus disease-2019 (COVID-19) involving both adult and pediatric patients. Herpes simplex virus (HSV) encephalitis is one of the most common causes of sporadic encephalitis. There have been cases of systemic and pulmonary reactivation of HSV due to immune dysregulation following COVID-19 infection. An 88-year-old woman diagnosed with Alzheimers disease was admitted to the intensive care unit (ICU) with fever and general condition disorder. On admission, the patient with fever and neck stiffness was found to be positive for HSV DNA in the cerebrospinal fluid (CSF) sample studied with lumbar puncture (LP) and positive for COVID polymerase chain reaction (PCR) in the nasopharyngeal swab sample taken together. While the COVID PCR test was positive in the CSF sample studied with LP performed on the 9th day of intensive care hospitalization, HSV DNA was found to be negative in the patient whose acyclovir treatment was continued. The COVID PCR test was also positive in the nasopharyngeal swab sample taken at the same time. Cardiac arrest occurred after sudden desaturation, and the patient was resuscitated for 6 min on the 11th day of ICU admission. Left frontotemporal epileptic activity in bedside electroencephalography was evaluated in favor of focal disorganization. In addition to frontotemporal lobe involvement, which is common in HSV and COVID-19 encephalitis, we want to report the coexistence of these two viruses. We believe that this case report should help professionals remind co-infections of HSV and severe acute respiratory syndrome coronavirus-2 to cure the morbidity appropriately.

Keywords: HSV encephalitis, COVID-19, CSF PCR, COVID-19 encephalitis