Encephalitis-predominant Nipah virus outbreaks in Kerala, India during 2024

Nipah virus (NiV) is a highly pathogenic zoonotic paramyxovirus with significant public health concern. Since 2018, Kerala, India, has experienced NiV outbreaks with variable clinical manifestations ranging from acute encephalitis syndrome (AES) to acute respiratory distress syndrome (ARDS). Recently, we observed two NiV outbreaks in Malappuram, Kerala, India during 2024, with AES as the predominant clinical manifestation in July and September 2024. Among all close contacts screened no secondary transmission of NiV was observed. The data from NiV outbreaks of Kerala state indicated that AES-predominant outbreaks (2019, 2021, and 2024) had shown no human-to-human transmission compared to ARDS-predominant outbreaks (2001, 2007, 2018, and 2023). Early detection, efficient containment, and improved surveillance were important measures in preventing secondary transmission. The two spill over events of NiV in 2024 reiterates the need for enhancing the surveillance of NiV among ARDS cases for timely case management and containment of the outbreak. In view of this, a network of seventeen Virus Research and Diagnostic Laboratories (VRDLs) was established for surveillance of severe acute respiratory illnesses in West Bengal and Kerala states of India. The continued public health preparedness and community awareness would help to prevent future outbreaks.