Late-onset Nipah virus encephalitis 11 years after the initial outbreak: A case report

Abstract

Nipah virus infection is known to cause late-onset and relapsed encephalitis, in addition to an acute encephalitic illness. This is a report of a 35 years old woman, who had exposure to the Nipah virus infection during the 1999 Malaysian outbreak, was positive for Nipah IgG by immunofl uorescence, and had multiple small hyperintense lesions in brain MRI typically seen in acute Nipah encephalitis patients, indicating asymptomatic Nipah virus infection. She subsequently developed acute encephalitis after 11 years, manifesting as diplopia, internuclear opthalmoplegia and epileptic seizures with pleocytosis in cerebrospinal fl uid examination. She had another episode of relapsed encephalitis a year later, with seizures, memory impairment, chorea and new lesions in MRI brain. This patient is unusual in the long incubation of 11 years before manifesting with late-onset Nipah encephalitis.