RESUMO
BACKGROUND: An outbreak of acute encephalitis syndrome (AES) was reported in Kerala in India in May 2011. The outbreak features were unusual in terms of seasonality, geographical distribution, age group, and clinical manifestations in comparison to the epidemiological features of Japanese Encephalitis. OBJECTIVE: To detect the etiology of the acute encephalitis syndrome outbreak. STUDY DESIGN: Investigation of outbreak was undertaken by collection of brief clinical history and epidemiological details along with the specimens for viral diagnosis. The serum/CSF samples (patients=208) received from the sentinel hospitals were subjected to IgM capture ELISA and RT-PCR specific for Japanese encephalitis (JE) virus and West Nile virus (WNV). The JE/WN IgM positive samples were further tested by serum neutralization assay for the presence of JE and WNV specific neutralizing antibody. RESULT: Most of the affected patients were aged above 15 years. No spatial clustering of the disease was noticed. Cases were observed in premonsoon and early monsoon season and in JE non-endemic area of Kerala. A total of 47 patient samples were positive for in-house JE IgM capture ELISA and WNV IgM capture ELISA. Serum neutralization assay result revealed that 32 of 42 (76.19%) sera were positive for WNV neutralization antibodies. WNV was isolated from a clinical specimen. Phylogenetic analysis of WNV envelope gene revealed 99% homology with Russian Lineage 1 WNV. CONCLUSION: West Nile virus (WNV) etiology was confirmed by virus isolation and detection of virus specific antibody from clinical specimen. Phylogenetic analysis grouped the current strain in lineage I West Nile virus.
Assuntos
Surtos de Doenças , Febre do Nilo Ocidental/epidemiologia , Vírus do Nilo Ocidental/isolamento & purificação , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Anticorpos Neutralizantes/sangue , Anticorpos Antivirais/sangue , Líquido Cefalorraquidiano/virologia , Criança , Pré-Escolar , Análise por Conglomerados , Ensaio de Imunoadsorção Enzimática , Feminino , Humanos , Imunoglobulina M/sangue , Índia/epidemiologia , Lactente , Recém-Nascido , Masculino , Pessoa de Meia-Idade , Filogenia , RNA Viral/genética , RNA Viral/isolamento & purificação , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Homologia de Sequência de Aminoácidos , Proteínas do Envelope Viral/genética , Viremia , Vírus do Nilo Ocidental/imunologiaRESUMO
An outbreak of viral encephalitis occurred in northern India in 2006. Attempts to identify an etiologic agent in cerebrospinal fluid by using reverse transcription-PCR showed positivity to enterovirus (EV) in 66 (21.6%) of 306 patients. Sequencing and phylogenetic analyses of PCR products from 59 (89.3%) of 66 specimens showed similarity with EV-89 and EV-76 sequences.