A Case Series of Powassan Meningoencephalitis in a Single Institution in Connecticut With One Case Resembling Herpes Simplex Virus (HSV) Meningoencephalitis on MRI.

Powassan virus (POWV) is a single-stranded RNA virus that belongs to the genus Orthoflavivirus, which is transmitted to humans through the bite of infected deer tick (Ixodes scapularis), with peak transmission during summer and fall. Most patients are asymptomatic; those who develop symptoms usually present with flu-like symptoms or neuroinvasive disease, including encephalitis, meningoencephalitis, or aseptic meningitis. The gold standard test for diagnosis is serological testing. The treatment is usually supportive care. In this case series, we have reported two cases that presented with fever, generalized weakness, and changes in mentation, later diagnosed with POWV meningoencephalitis. The magnetic resonance imaging (MRI) findings in the first case were suggestive of herpes simplex virus (HSV), imposing a diagnostic challenge. Patients might end up with cognitive impairment, speech difficulties, headaches, imbalance, and ophthalmoplegia as long-term consequences, and both of our cases had cognitive impairment, and one case had weakness, requiring further neuropsychiatry evaluation, as well as physical therapy. Although cases of POWV encephalitis are very rare, these cases describe the importance of serological testing for POWV, especially in endemic areas, in patients with a known or unknown history of tick bite.