Nipah Virus: Human Immune Responses, Transmission Mechanisms, and Vaccine Development

Nipah virus (NiV) is a zoonotic paramyxovirus that causes severe disease in humans, characterized by encephalitis and respiratory symptoms with high mortality. First identified in a 1998–99 outbreak in Malaysia, NiV has since caused sporadic outbreaks in South Asia with case fatality rates ranging from ~40% to 75%. Human infection typically results from spillover of the virus from its natural reservoir, fruit bats of the Pteropus genus. Human-to-human transmission can occur, especially with the NiV-Bangladesh strain, raising pandemic concerns despite NiV’s limited sustained transmissibility. This systematic review examines the human immunological response to NiV infection and its interplay with pathogenesis, discusses the mechanisms of NiV transmission from bats to humans and among humans, and reviews the current landscape of NiV vaccine development. NiV has evolved multiple strategies to evade innate immunity, and an effective immune response (involving both robust interferon activity and adaptive responses) is critical for host survival. Major transmission pathways include bat-to-human (e.g. via contaminated date palm sap), animal-to-human (e.g. via pigs or horses), and close-contact spread, which have been implicated in several outbreaks. Finally, I summarize progress in NiV vaccine research: several vaccine candidates (e.g., viral-vectored, subunit, and mRNA-based vaccines) have demonstrated protective immunity in preclinical models and are in Phase 1 trials. Given the rarity of outbreaks, innovative regulatory strategies are being pursued to expedite vaccine availability. Overall, strengthening our understanding of NiV immunity and transmission, alongside advancing vaccines, is pivotal to reduce the threat of this deadly virus.