Summary
A medRxiv preprint assesses where Japanese encephalitis virus circulated in Australia during 2021–23 and where environmental conditions were suitable for transmission. It identifies northern floodplains and inland eastern areas as regions with both high estimated suitability and strong evidence of circulation.
A medRxiv preprint maps Japanese encephalitis virus (JEV) transmission and environmental suitability across Australia during the 2021–23 outbreak. The researchers combined national surveillance records with estimates of habitat suitability and host densities. They found that floodplain wetlands in northern Australia and inland eastern Australia had both high estimated suitability for transmission and the strongest evidence of virus circulation.
The assessment follows a period when JEV, previously detected in only sporadic outbreaks in Australia’s tropical north, was identified in 45 people and more than 85 piggeries. Detections were also reported in feral pigs, mosquitoes and other livestock, including in the temperate far south. JEV is a leading cause of viral encephalitis in humans in Asia.
Separating detected transmission from environmental suitability
The researchers describe two related but distinct areas. The “realised niche” is the estimated spatial extent of transmission during the outbreak, based on surveillance and detection. The “potential niche” is the area the analysis identifies as environmentally suitable for transmission. A place can be suitable without the study having evidence that transmission occurred there.
To assess these patterns, the team assembled 2021–23 detections in humans, mosquitoes, domestic pigs, feral pigs and sentinel chickens. They combined those records with previously published habitat-suitability predictions for vertebrate hosts and mosquito vectors, plus estimated densities of humans, domestic pigs and feral pigs.
The resulting assessment projected broad environmental suitability across much of northern and eastern Australia. Within that broad area, northern floodplains and the inland east stood out because the modelled suitability coincided with stronger evidence of circulation. This distinction can help public-health teams interpret where ecological conditions may support transmission alongside where surveillance has detected the virus.
What the assessment covers
The findings describe the 2021–23 outbreak period and a modelled assessment of environmental suitability; they are not a forecast of future case numbers. The report is a medRxiv preprint, and its findings are presented here as preprint research.