West Nile virus (WNV) is a mosquito-borne RNA flavivirus and human neuropathogen. The overall mortality rate for WNV disease is < 0.1% for all patients infected with WNV. Most WNV-related morbidity and mortality results from neurologic and respiratory involvement. For patients with WNV encephalitis, the mortality rate ranges from 12% to 15% and can range from 10- 30% for patients with West Nile neuroinvasive disease. Mortality rates can reach up to 50% for patients presenting with acute flaccid paralysis and respiratory failure. We report a fatal case of meningoencephalomyelitis due to chronic WNV infection in a 21-year-old male who presented with muscle weakness progressing to ascending paralysis and respiratory distress requiring mechanical ventilatory support. He was diagnosed with acute motor axonal neuropathy, a GBS variant, and had a prolonged hospital course until he died 8 months after the onset of symptoms. Microscopic examination of the central nervous system samples collected during autopsy revealed meningoencephalomyelitis. Subsequent serologic testing revealed antibodies to WNV, and immunohistochemistry detected presumed WNV antigens in neurons in multiple foci in the cerebrum, cerebellum, brainstem, and spinal cord, later confirmed by an in situ hybridization technique. Myelitis and motor neuron degeneration in the spinal cord with subsequent atrophy in skeletal muscle were also observed. Our case exemplifies chronic WNV infection-causing meningoencephalomyelitis that manifested clinically as acute motor axonal peripheral neuropathy. WNV-associated encephalomyelitis, as well as peripheral neuropathy, should be considered in patients presenting with muscle weakness and paralysis, especially when occurring in known endemic regions.

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