A multi-scale approach to understanding and predicting spillover of an emerging infectious disease of bat origin

Background/Question/Methods

Hendra virus is a fatal zoonotic virus that spills over from Australian fruit bats (Pteropus spp.) to domestic animals and humans. Spillover events are relatively rare in both space and time, but when they occur they have major medical, social and economic consequences.  We assess the ecology of Hendra virus at multiple scales—from viral dynamics within individuals, to viral dynamics at metapopulation and landscape scales, to the overarching effect of season, climate and environmental change on disease transmission.  We evaluate how risk-factors interact across scales to potentially drive spillover events in domestic animals (for example, stress influences within-host viral replication and shedding, yet may be driven by environmental perturbations at the landscape or global scale). 

Results/Conclusions

Two divergent, but not mutually exclusive, hypotheses emerged as likely explanations for Hendra virus spillover into domestic animals and humans.  First, at the within-host level, increased viral shedding by particular demographic groups of bats, or periods of increased shedding in all bats in response to environmental stress, may drive a higher force of infection to novel hosts.  Second, transmission dynamics at the metapopulation and landscape scales may drive pulses of infection at local scales.  We discuss the implications of these hypotheses within the conceptual framework of a multi-scale and multi-disciplinary approach to understanding emerging infectious diseases.