Ten year clinical and serological outcomes of Nipah virus infection

Background and Objective: Nipah virus is an emerging zoonotic virus which caused fatal outbreak among Malaysian pig-farmers in 1998-1999. The Nipah virus outbreak represented one of the batderived paramyxoviruses that have emerged during the last decade to cause severe human and animal disease. Long-term neurological assessments and serological pattern descriptions are limited. We assessed persistent symptoms, neurological and functional outcome of 36 Nipah virus infection survivors after 10 years of the outbreak in Malaysia. Their serological pattern of Nipah virus for both IgM and IgG were studied. Methods: During September 2008 and March 2009, we administered a questionnaire on persistent symptoms and functional disability for all the Nipah virus infection survivors and Nipah infection contacts. Blood were collected for serological test for Nipah virus IgM and IgG. Results: A total of 70 subjects were included in the study, 39 of whom had virus Nipah infection in the past. Among the Nipah virus infection survivors, 31 (79%) were male; mean age was 46 + 1.8 years. Sixteen Nipah infection survivors (41%) were asymptomatic. The most common persistent clinical features were fatigue (12, 31%), daytime somnolence (10, 26%) and focal neurological deficits (8, 21%). Five out of 13 (38%) Nipah encephalitis survivors had significant disability on the modified Rankin scale. Serologically, all subjects were tested negative on the Nipah IgM serology test. IgG were positive for 39 subjects in which 3 had asymptomatic infection during the outbreak. Conclusion: Persistent fatigue and daytime somnolence were common disabling symptoms after 10 years of Nipah virus infection, seen in those with previous encephalitis as well as non-encephalitic infection. Serologically all patients had negative Nipah IgM but positive IgG after 10 years of illness. Neurology Asia 2009; 14 : 53 – 58 Address correspondence to: Dr HT Chong, c/o Neurology Laboratory, University Malaya Medical Centre 59100 Kuala Lumpur, Malaysia. E-mail: [email protected] INTRODUCTION Between 1998 and 1999, an outbreak of viral encephalitis involving more than 260 reported cases with over 100 fatalities occurred in West Malaysia especially among pig farm workers in the states of Perak and Negeri Sembilan.15 Although Japanese encephalitis virus was initially implicated as the main causative agent for this outbreak, epidemiological and laboratory investigations subsequently discovered Nipah virus as the aetiologic pathogen.5 Named after the village of Kampung Baru Sungai Nipah in Negri Sembilan where it was first isolated, the Nipah virus is a member of the Paramyxoiridae family, related to but distinct from Hendra virus which is also associated with a zoonotic virus.6 The main presenting features were fever, headache, dizziness, and vomiting. In the initial outbreak, 55% 61% had a reduced level of consciousness and prominent brain-stem dysfunction. Distinctive clinical signs included segmental myoclonus, areflexia and hypotonia, hypertension, and tachycardia and thus suggested the involvement of the brain stem and the upper cervical spinal cord among other areas of central nervous system.2, 7 Serology plays an important role in the diagnosis of Nipah virus infection. In one Malaysian study at least 76% of Nipah patients have positive serology for Nipah virus during the acute illness.2, 8 However, the long term clinical and serological outcome of Nipah infection is poorly studied.9 This study aims to look at persistence of serology and to analyze the Nipah survivors in terms of their persistent clinical symptoms, clinical state and neurological outcome 10 years after the initial outbreak.