Epidemiological Linkages and Risk Behaviors for Secondary Transmission among Suspected Nipah Virus Cases During Recurrent Spillover Events in Malappuram District, Kerala
Priya Chandran, Jayakrishnan Thavody, C. M. Sujina, K. A. Jasmine, P. V. Shiji, Sabitha Rose Jacob, S. Anisha, M. S. Amritha, Remiza R AnswarBackground:
Nipah virus (NiV) infection is a bat-borne zoonotic disease with high case fatality rates. Transmission to humans occurs through direct or indirect contact with infected bats and pigs; person-to-person transmission has been reported in outbreaks in West Bengal and Kerala. Between the years 2024 and 2025, Malappuram district, Kerala state, experienced four lab-confirmed zoonotic spillover events. Therefore, this study aims to describe the epidemiological linkages and behavioral risk factors for secondary transmission of suspected NiV infection cases identified during recurrent spillover events in Malappuram district, Kerala.
Materials and Methods:
All individuals satisfying the case definition of “suspect case” of NiV infection were investigated for epidemiological links to the index case, tested for NiV, and followed up for the duration of the surveillance period.
Results:
Across the four spillover events, our institution admitted 29, 24, 29, and 28 suspect cases, respectively. Most exposures occurred in households and hospital settings. No exposed contact developed confirmed NiV infection. The absence of secondary cases in all four events may be attributable to the encephalitic presentation of the index case, early diagnosis, and prompt isolation.
Conclusion:
Household caregivers and healthcare professionals are more at risk of exposure to the confirmed case due to the close nature of contact during the late stage of the disease. Early isolation and infection prevention practices may have contributed to the absence of secondary cases.