Long-term neurological and functional outcome in Nipah virus infection

Objective: Nipah virus (NiV) is an emerging zoonosis. Central nervous system disease frequently results in high case-fatality. Long-term neurological assessments of survivors are limited. We assessed long-term neurologic and functional outcomes of 22 patients surviving NiV illness in Bangladesh. Methods: During August 2005 and May 2006, we administered a questionnaire on persistent symptoms and functional difficulties to 22 previously identified NiV infection survivors. We performed neurologic evaluations and brain magnetic resonance imaging (MRI). Results: Twelve (55%) subjects were male; median age was 14.5 years (range 6-50). Seventeen (77%) survived encephalitis, and 5 survived febrile illness. All but I subject had disabling fatigue, with a median duration of 5 months (range, 8 days-8 months). Seven encephalitis patients (32% overall), but none with febrile illness had persistent neurologic dysfunction, including static encephalopathy (n = 4), ocular motor palsies (2), cervical dystonia (2), focal weakness (2), and facial paralysis (1). Four cases had delayed-onset neurologic abnormalities months after acute illness. Behavioral abnormalities were reported by caregivers of over 50% of subjects under age 16. MRI abnormalities were present in 15, and included multifocal hyperintensities, cerebral atrophy, and confluent cortical and subcortical signal changes. Interpretation: Although delayed progression to neurologic illness following Nipah fever was not observed, persistent fatigue and functional impairment was frequent. Neurologic sequelae were frequent following Nipah encephalitis. Neurologic dysfunction may persist for years after acute infection, and new neurologic dysfunction may develop after acute illness. Survivors of NiV infection may experience substantial long-term neurologic and functional morbidity.