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 bat-derived 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.