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Published on: March 13, 2018
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West Nile encephalitis outbreak in Kerala, India, 2011
B Anukumar1, Gajanan N Sapkal2, Babasheb V Tandale2
1National Institute of Virology, Kerala, Govt. T. D. Medical College Hospital, Alappuzha 688005, Kerala, India.
Summary
West Nile virus (WNV) caused an unusual acute encephalitis syndrome (AES) outbreak in Kerala, India. Virus isolation and antibody detection confirmed WNV etiology, with phylogenetic analysis linking it to lineage I strains.
Area of Science:
- Epidemiology
- Virology
- Infectious Diseases
Background:
- An unusual outbreak of acute encephalitis syndrome (AES) occurred in Kerala, India, in May 2011.
- The outbreak presented atypical seasonality, geographical distribution, age demographics, and clinical features compared to Japanese Encephalitis.
Purpose of the Study:
- To determine the etiological agent responsible for the acute encephalitis syndrome outbreak in Kerala.
Main Methods:
- Collected clinical and epidemiological data from 208 patients.
- Utilized IgM capture ELISA and RT-PCR for Japanese encephalitis (JE) virus and West Nile virus (WNV) detection in serum/CSF samples.
- Performed serum neutralization assays to confirm JE and WNV specific antibodies.
Main Results:
- The majority of affected individuals were over 15 years old, with no spatial disease clustering observed.
- Cases occurred during the pre-monsoon and early monsoon seasons in a JE non-endemic region.
- 47 samples tested positive for JE or WNV IgM; 32 of 42 confirmed WNV-specific neutralizing antibodies. WNV was isolated and phylogenetically identified as lineage I.
Conclusions:
- West Nile virus (WNV) was confirmed as the causative agent of the AES outbreak through virus isolation and specific antibody detection.
- Phylogenetic analysis placed the isolated WNV strain within lineage I.
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