Pune, 30th September 2026: Researchers from National Institute of Virology (NIV) have detected Genotype I (GI) of the Japanese encephalitis virus (JEV) in mosquitoes in Assam. The finding provides evidence of the virus circulating in Culex mosquitoes and highlights the need for regular surveillance to monitor its spread.
The study identified the virus in three groups of Culex tritaeniorhynchus mosquitoes collected from Assam’s Kamrup district. The investigation followed the detection of Japanese encephalitis infections among pigs in the district in May 2025. Researchers subsequently conducted an entomological survey to assess mosquito density and investigate the presence of the virus.
During the investigation, researchers collected 858 mosquitoes from the affected area. Of these, 521 (60.7%) were adult female Culex mosquitoes, with Culex tritaeniorhynchus being the most commonly identified species.
The collected mosquitoes were divided into 20 groups and tested using the reverse transcription polymerase chain reaction (RT-PCR) method.
Three groups of Culex tritaeniorhynchus tested positive for the Japanese encephalitis virus. Further genetic analysis confirmed that the virus belonged to Genotype I (GI), which showed similarities to strains reported internationally.
The study was published in the American Journal of Tropical Medicine and Hygiene. Researchers Surendra Kumar, R. Balasubramanian, Prajwal Gaikwad and Dr Naveen Kumar from NIV, Pune, were among those involved in the research.
The detection of the virus in mosquitoes in Assam has highlighted the need for continuous monitoring of mosquito populations and virus circulation. Researchers have emphasised the importance of integrated vector control measures and a One Health-based surveillance system that considers human, animal and environmental health.
Dr Mahendra Jagtap, a state entomologist, said, "The Japanese encephalitis virus is already known to circulate among mosquitoes and animals, including domestic animals, horses and pigs. It is commonly found in wetlands and paddy fields, where mosquitoes breed. In Maharashtra, cases are relatively limited, except in Nagpur, and some are linked to migration from other states. The disease is also reported in Madhya Pradesh and Uttar Pradesh, where children account for a higher number of cases and deaths."
The findings underline the importance of monitoring mosquito populations and identifying changes in the circulation of the virus. Regular surveillance and timely interventions could help public health authorities track the virus and strengthen disease prevention measures.
