Powassan virus has been reported with varying degrees of neurological sequelae. Symptoms range from fever and headaches to severe encephalopathy with neurologic deficits and seizures. Intracranial hemorrhage has been documented in two case reports. We report the first known case of Powassan viral hemorrhagic encephalitis in Pennsylvania.

A 69-year-old man was hospitalized with encephalopathy, diplopia, and difficulty ambulating preceded by three days of fevers, chills, and myalgias. He had a temperature of 102.4 degrees Fahrenheit on admission and physical examination revealed a macular blanching rash on his torso. Upon admission, he was lethargic, disoriented, and unable to name objects or repeat sentences. He had a left gaze preference, right visual field deficit, and bilateral postural tremor. Computed tomography (CT) of the head was negative for acute findings. Cerebrospinal fluid testing was negative for infectious etiology, but showed pleocytosis and significant protein elevation. He was treated empirically for bacterial and viral infection with antibiotics, anti-virals, and intravenous immunoglobulins. The patient improved clinically and was discharged to rehabilitation, however, one week later he was found obtunded while having a generalized seizure. CT of the head revealed a large left frontal parenchymal hematoma with intraventricular extension. The patient’s family withdrew care due to severity of the bleed and poor prognosis for functional neurological recovery. Subsequently Powassan virus IgM on serum testing resulted as positive. 

Powassan virus is a poorly studied member of the Flavivirus family, endemic to the Northern United States. It may be underdiagnosed in favor of other viral etiologies of encephalitis. Clinical course can be biphasic with an initial prodrome of mild symptoms followed by a severe meningoencephalitis. Hemorrhagic complications have been documented in sporadic case reports though no preferential area of hemorrhagic involvement is seen. We describe the first case of hemorrhagic encephalitis from Powassan virus in Pennsylvania.