Background
Varicella, commonly known as chickenpox is a neglected disease in India with numerous outbreaks reported in the last decade. Unfortunately, varicella vaccine is not included in India’s Universal Immunization Program (UIP), and active surveillance is not in place. Investigation of suspected varicella cases from various Indian regions was done to understand disease burden and molecular epidemiology.
Methods
Between 2016 and 2025, 195 clinical cases from suspected chickenpox cases were referred for virological investigation from five States and one Union Territory of India. Samples were analyzed for Varicella-Zoster Virus (VZV) using IgM-EIA and/or conventional PCR. Virus isolation was attempted on Vero, MRC-5, and WI-38 cell lines. PCR-positive products were sequenced for phylogenetic analysis to identify circulating VZV clades.
Results
Of the 195 suspected cases, 159 (81.53 %) were confirmed by serological or molecular methods. Majority of the cases (n = 152, 77.94 %) occurred in individuals under 18 years of age, with higher incidence among males (n = 119) than females (n = 76). Of 58 diverse clinical specimens, 43 showed VZV DNA. Sequencing of representative PCR products showed circulation of VZV clade-5 in 29 cases and clade-9 in a single case. Unfortunately, attempts at VZV isolation were not successful.
Conclusion
The study confirms a high laboratory-confirmed rate of varicella among suspected cases in India, with children being the most affected. Molecular data identified VZV clade-5 as primary circulating genotype. These findings highlight a significant burden of chickenpox and provide molecular evidence to support inclusion of the varicella vaccine in India’s Universal Immunization Program.
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