Abstract
BackgroundThe aetiological spectrum of acute encephalitis shows inter- and intra-geographical variations. We aimed to identify the viruses that cause infectious encephalitis in Sri Lanka, which represents a South Asian population.MethodsA cross-sectional study was conducted among 99 patients with encephalitis/meningoencephalitis admitted to two tertiary-care hospitals in Colombo. Cerebrospinal fluid and serum were tested for conventional and emerging encephalitogenic viruses. Specific nucleic acid amplification and antibody assays were used to identify viruses. Plaque reduction neutralization test was done to confirm the diagnosis of West Nile virus (WNV).ResultsPatients’ age ranged from 1 month to 73 years (mean = 24.91; SD = 21.33) with a male:female ratio of 1.75:1. A viral aetiology was identified in only 27.3%. These included dengue virus (40.7%), Japanese encephalitis virus (25.9%), varicella zoster virus, WNV and probable Epstein Barr virus (11.1% each). None were positive for herpes simplex viruses or cytomegalovirus. Screening for bacterial aetiologies was negative for all patients. There were no distinguishable clinical or laboratory findings between the different viral aetiologies. The case fatality rate was 7%, which was higher among patients with an identified viral aetiology.ConclusionsA viral aetiology was identified in only about a quarter of patients with encephalitis. Dengue virus accounted for the majority.
Highlights
The aetiological spectrum of acute encephalitis shows inter- and intra-geographical variations
This study aimed to identify the viruses causing encephalitis in Sri Lanka to add to the spectrum of encephalitic viruses being identified in South Asia
Most cases peaked during the months of January/February and May/June consistent with the temporal pattern of encephalitis noted in Sri Lanka (Fig. 1)
Summary
The aetiological spectrum of acute encephalitis shows inter- and intra-geographical variations. We aimed to identify the viruses that cause infectious encephalitis in Sri Lanka, which represents a South Asian population. The causes of encephalitis are diverse, but broadly categorised as infectious and autoimmune. Viruses are the most commonly identified aetiology of the infectious agents [2], but in up to 70% of cases the cause remains unidentified [3]. Herpes simplex virus type 1 (HSV1) is reportedly the commonest cause of adult sporadic encephalitis while varicella zoster virus (VZV) account for most of paediatric encephalitis in developed countries [5, 6]. Apart from the established encephalitic viruses, recent studies have identified many emerging encephalitic viruses such as Chandipura and Nipah viruses, in South Asia [9, 10]. In Sri Lanka, which is a tropical island positioned
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