Nipah encephalitis outbreak in Malaysia, clinical features in patients from Seremban

Background: An outbreak of viral encephalitis occurred among pig industry workers in Malaysia in September 98 to April 1999. The encephalitis was attributed to a new paramyxovirus, Nipah virus. This is a description of the clinical features of 103 patients treated in the Seremban Hospital with characterization of the prognostic factors. Methods: Clinical case records and laboratory investigations were reviewed. The case definition was: patients from the outbreak area, direct contact or in close proximity with pigs, clinical or CSF features of encephalitis. Results: The mean age was 38 years, 89 % were male, 58 % were ethnic Chinese, 78 % were pig farm owners or hired workers. The mean incubation period was 10 days. The patients typically presented with non-specific systemic symptoms of fever, headache, myalgia and sore throat. Seizures and focal neurological signs were seen in 16% and 5 % respectively. In the more severe cases, this was followed by drowsiness and deteriorating consciousness requiring ventilation in 61%. Autonomic disturbances and myoclonic jerks were common features. The mortality was high at 41%. Systolic hypertension, tachycardia and high fever were associated with poor outcome. On the other hand, 40 % recovered fully. As for the other 19%, the residual neurological signs were mostly mild. Conclusion: Nipah virus caused an encephalitis illness with short incubation period and high mortality. The prognosis for the survivors was good