Hendra virus review details spillover history and new variant challenges

Since 1994, Hendra virus has caused recurrent cross-species spillover events in Australia. It is a highly lethal zoonotic henipavirus with tropism for vascular endothelial and neural tissues, which makes it important to both veterinary medicine and public health. A review published on 19 August 2026 in Frontiers in Veterinary Science gathers the research progress on the virus from a veterinary-oriented One Health perspective.

The transmission chain is known: flying foxes, bats of the genus Pteropus, are the natural reservoir hosts, and horses act as intermediate and amplifying hosts. All confirmed human infections have occurred through horses. Human infection is rare but can cause severe respiratory and neurological disease. The review records that detection of antibodies and RNA of related henipaviruses in Southeast Asian bats indicates regional diversity and a possible broader henipavirus spillover risk but, according to the authors, does not demonstrate Hendra virus circulation or transmission in that region.

The text covers viral biology, transmission, clinical disease, diagnostics, animal models, equine vaccination and clinical-stage vaccines and antibody-based interventions. Two points receive particular attention: the diagnostic challenges associated with the virus's genotype 2, HeV-g2, and the role of horse vaccination in reducing occupational exposure for veterinarians and handlers.

The variant's story was told in two Emerging Infectious Diseases papers in 2022. In the first, Australian researchers identified and isolated, from a horse in Queensland that died of acute illness with signs consistent with Hendra, a variant not detected by routine testing. Whole-genome sequencing showed about 83% nucleotide identity with the prototypic virus. In silico and in vitro comparisons of the receptor-binding protein indicated that the human monoclonal antibody m102.4, used for post-exposure prophylaxis, and the current equine vaccine should be effective against the variant. An updated quantitative PCR for routine surveillance resulted in subsequent case detection, and genetic consistency with virus detected in grey-headed flying foxes suggested the variant circulates at least in that species. The authors recommended updating surveillance and biosecurity to acknowledge risk across all regions frequented by flying foxes.

The second paper closed the link: the genotype 2 variant was detected in the urine of black and grey-headed flying foxes, which is the pathway relevant for spillover, supporting an expanded geographic range of Hendra virus risk to horses and humans.

For the equine clinician outside Australia, the interest is methodological: a virus known for three decades still managed to escape routine tests, and the response combined sentinel surveillance in horses, sequencing, PCR revision and verification that vaccine and antibody remained valid. The 2026 review, open access, gathers the references for anyone wishing to retrace that path.