Powassan Virus Encephalitis in an Immunocompromised Patient: A Diagnostic Challenge With Case Report and Literature Review.

Powassan virus (POWV) is a tick-borne flavivirus transmitted to humans by Ixodes ticks. In this report, we describe an immunocompromised patient who presented with progressive neurologic symptoms and was diagnosed with POWV encephalitis. Additionally, the patient tested positive for Jamestown Canyon virus (JCV), a mosquito-borne orthobunyavirus, creating a diagnostic dilemma. This case underscores the importance of considering vector-borne illnesses in immunocompromised individuals who present with neurologic symptoms, particularly during peak arboviral transmission seasons in the United States. It also highlights the complexities of laboratory testing for arboviral infections in these vulnerable patients.