Eloise B. Skinner

Background: The emergence of Japanese encephalitis virus (JEV) in Australia raises questions about transmission potential across neighbouring Pacific Island countries and territories (PICs), where surveillance infrastructure and diagnostic capacity are limited. Methodology: We conducted a qualitative risk assessment of 22 PICs structured around three components: (1) ‘release assessment’, evaluating JEV introduction pathways based on geographic proximity, migratory waterbird flyway connectivity, and windborne mosquito dispersal potential; (2) ‘exposure assessment’, evaluating ecological transmission suitability based on vector and host competence and occurrence; and (3) ‘risk characterisation’, integrating release and exposure components to stratify countries into transmission risk profiles (endemic, epidemic, and low potential). Introduction potential varied across the region, with northern and western PICs having greatest connectivity to endemic regions. Ecological suitability for transmission was sufficient to support JEV transmission in 13 of the 22 PICs if introduced. Eight PICs were characterised as having endemic transmission potential (Papua New Guinea, which already has confirmed circulation, Solomon Islands, New Caledonia, Vanuatu, Fiji, Palau, Guam, and Northern Mariana Islands), based on diverse competent vector communities, high ardeid waterbird diversity, and moderate-to-high introduction potential. Five PICs (Federated States of Micronesia, Tonga, Samoa, Tuvalu, and Nauru) were characterised as having epidemic transmission potential, supported by pig densities capable of amplifying viral titres and sufficient vector diversity, but lacking ardeid populations necessary to sustain endemic cycles. The remaining nine PICs had low transmission potential due to limited vector and host communities. These risk stratifications are relative; the absolute probability of JEV establishment in any PIC remains uncertain. Conclusions: Distinct transmission profiles require differentiated public health responses, from sustained surveillance in endemic-potential settings to early detection and rapid outbreak response in epidemic-potential settings. Regional coordination through shared diagnostic networks and vaccine access pathways is critical to support preparedness before JEV becomes established across the Pacific.

Background: Empirical surveillance for Aedes-borne arboviruses is inherently reactive, detecting transmission after it has commenced. For small island settings where dengue and chikungunya circulate sporadically, characterising when and where environmental conditions could support local transmission is critical for preparedness. In Mauritius, Aedes albopictus is the sole primary vector for dengue and chikungunya viruses, but previous suitability assessments have relied on Aedes aegypti parameterisation. Methods: We estimated monthly Index P for dengue and chikungunya across 160 localities in Mauritius from January 2014 to October 2024. Index P, a mechanistic transmission suitability measure derived from the Ross-Macdonald framework that climate-dependent transmission potential attributable to one adult female mosquito. Mean temperature and relative humidity were derived from ERA5-Land reanalysis dataset via Google Earth Engine and incorporated within the Mosquito-borne Viral Suitability Estimator (MVSE) framework. Index P was also parameterised with Ae. albopictus-specific biological priors and virus-specific vector competence values for both dengue and chikungunya. Results: Transmission suitability for both viruses was concentrated within the austral summer (November to April), with near-zero values in winter, below the indicative transmission threshold (Index P ≥ 0.5). Chikungunya exhibited consistently higher, more spatially widespread and longer-lasting suitability than dengue: all districts exceeded the transmission suitability threshold for chikungunya (Index P = 0.71), while median dengue Index P = 0.24, remaining below this threshold, during the same study period. Dengue peak suitability was concentrated in western coastal localities, consistent with the greater thermal sensitivity of its extrinsic incubation period in Ae. albopictus. Conclusions: These findings indicate that dengue and chikungunya have distinct, virus-specific climate-suitability profiles in Mauritius, and should not be treated as interchangeable for preparedness purposes. This provides an important Ae. albopictus-parameterised evidence base for Mauritius, enabling seasonal and geographic targeting of surveillance and vector control ahead of, rather than in response to local transmission.

Malaria eradication requires reducing transmission in endemic areas and maintaining these reductions in areas where elimination has been achieved. In Altamira, a municipality in the Xingu Basin of the Brazilian Amazon, a malaria control program was implemented during the construction of the Belo Monte Dam which eliminated local malaria cases, but resurged in rural areas after these efforts ceased. To elucidate different drivers of malaria transmission in Altamira, before (2006–2012) and after (2017–2020) the construction of Belo Monte Dam and the localized malaria control program, we analyzed annual notified malaria cases alongside geospatial variables including forest edge, population size and travel time to urban centers. Due to the low incidence, malaria case data was clustered based on the geographic proximity of health centers. A total of 17,578 malaria cases were reported in Altamira between 2006 and 2020. Malaria cases exceeded 1,200 per year prior to dam construction, then dropped below 100 during construction, resurging to over 700 cases by 2020 predominantly in rural clusters. Using generalized additive models we found that malaria cases increased significantly with increases in forest edge habitats and local population size, both before and after dam construction, while neither distance to deforestation nor climatic variables explained incidence variation. This study emphasizes that interruptions to control efforts, even when localized, can rapidly reverse gains, and that understanding landscape epidemiology is critical for achieving and maintaining malaria elimination in Amazonian settings.

SUMMARY: Ross River virus (RRV) causes the most mosquito-borne disease notifications in Australia and a considerable burden of non-fatal, yet frequently prolonged rheumatic illness across the Australia-Pacific region, reflected in thousands of notifications each year and notable economic and quality-of-life losses. Research on RRV spans multiple disciplines, encompassing viral genomics, immunopathology, transmission ecology, epidemiology, entomology, and environmental science. This review synthesizes two decades of cross-disciplinary investigations to present an integrated perspective on the biological, clinical, ecological, and environmental dimensions of RRV infection. By consolidating findings from diverse fields, the review enhances understanding of the complex factors influencing RRV transmission and disease outcomes throughout its endemic range.

Malaria eradication requires reducing transmission in endemic areas and maintaining these reductions in areas where elimination has been achieved. In Altamira, a municipality in the Xingu Basin of the Brazilian Amazon, a malaria control program was implemented during the construction of the Belo Monte Dam which eliminated local malaria cases, but resurged in rural areas after these efforts ceased. To elucidate different drivers of malaria transmission in Altamira, before (2006-2012) and after (2017-2020) the construction of Belo Monte Dam and the localized malaria control program, we anlayzed annual notified malaria cases alongside geospatial variables including forest edge, population size and travel time to urban centres. Due to the low incidence, malaria case data was clustered based on the geographic proximity of health centers. A total of 17,578 malaria cases were reported in Altamira between 2006 and 2020. Malaria cases exceeded 1,200 per year prior to dam construction, then dropped below 100 during construction, resurging to over 700 cases by 2020 predominantly in rural clusters. Using generalized additive models we found that malaria cases increased significantly with increases in forest edge habitats and local population size, both before and after dam construction, while neither distance to deforestation nor climatic variables explained incidence variation. This study emphasizes that interruptions to control efforts, even when localized, can rapidly reverse gains, and that understanding landscape epidemiology is critical for achieving and maintaining malaria elimination in Amazonian settings.

Japanese encephalitis virus (JEV) is a multi-vector, multi-host pathogen maintained in circulation between Culex mosquitoes and waterbirds, with occasional spillover to humans. In Australia, sporadic local transmission of JEV was historically confined to northern Australia until 2021 after which outbreaks occurred for the first time in temperate southern regions in 2022 and 2023, respectively. Following this outbreak, there have been concerns that JEV has potentially become endemic in Australia, posing an ongoing public health risk exacerbated by shifting climatic and environmental factors. We developed and applied a spatially explicit spillover modelling framework which focuses on estimating i) an ecological suitability index for JEV in Australia and, ii) the spillover potential to human populations if endemic transmission is established. To calculate ecological suitability and the potential number of humans that could be exposed, we integrated the ecological and epidemiological conditions that would allow JEV to circulate in Australia and spillover to human populations. An ecological suitability index was calculated by combining the presence of hosts ( Ardeidae birds, domestic piggeries, feral pigs) and vectors ( Culex annulirostris and Culex quinquefasciatus ), host-vector contact rates, and vector infection and transmission potential for JEV at a 1km resolution. JEV spillover potential was estimated by multiplying the ecological suitability index with human population density. We used this estimate to calculate the total population that could be exposed to JEV at the Local Government Area (LGA) level and State/Territory level. We validated our estimates by calculating a population-weighted mean value for each LGA and compared the values between LGAs with confirmed JEV clinical cases to those without. We found an elevated ecological suitability along the east coast and south-western coast of Australia, inland from the northern centre of the country, and surrounding the Murray River Basin (along the border of New South Wales and Victoria). If JEV becomes established in ecologically suitable areas, high spillover potential to humans would exist along Australia’s eastern coast. This exposure potential extends inland to areas like the Murray River Basin, which provide ample habitat for enzootic hosts and vector species. High spillover potential also exists in the Northern Territory, along the southwestern coast of Western Australia, and in South Australia. LGAs with historically confirmed clinical cases in humans had a statistically higher population-weighted mean value compared to those without confirmed cases, supporting the model’s capability to differentiate highly suitable areas. By integrating vector-host dynamics and human population density into a spatially explicit framework, we identified areas with high JEV ecological suitability and the potential for spillover into human populations if transmission of JEV were to become established. The results were driven by interactions between vectors, hosts and vector competence. These findings provide insights for targeted surveillance and vector control strategies in Australia. Proactive and sustained interventions are essential to mitigate JEV’s growing threat and to protect vulnerable populations in the face of ongoing environmental changes.

Rising temperatures can expand malaria transmission into higher altitudes. This is relevant for the projection of future resource needs to sustain malaria control. In Papua New Guinea (PNG), malaria transmission is intense at low altitudes, but new infections are rarely acquired above 1600 m. The present study applied the basic reproduction number (R ₀ ) over temperature to assess changes in malaria transmission ranges in PNG over past decades (1960 to 2019) and in the near future by using satellite-based temperature data and climate projections for 2021 to 2040. The analysis considered geographic range shifts for malaria temperature suitability, the resulting changes in the population at risk and effectiveness of interventions. Malaria temperature suitability ranges have subtly changed between 1960 and 2019, with the proportion of people living in suitable areas increasing from 58% to 61% (equivalent to 249,125 people). Under a conservative climate change model, this proportion is expected increase to 74% by 2040 (equivalent to 2,802,709 people). Interventions had a larger impact on malaria incidence in areas with R ₀ <0.3, mitigating the current and future impact of climate change. Nevertheless, the number of people requiring access to malaria control is expected to double by 2040, to 13.4 million with 2.8 million attributed to climate change alone. The impacted areas are densely populated highlands regions with a more susceptible population and an increased potential for epidemics and clinical disease. These findings underscore the challenges of climate change for malaria elimination in PNG and highlight the need to accurately guide preparedness and forecast the additional resource requirements. Key Findings: Climate change and population growth are predicted to double the number of people at risk of malaria by 2040 The altitude limit for malaria transmission will shift by about 300 m by 2040 as compared to 1960. Current control strategies had a much higher impact to sustainably reduce malaria incidence at higher altitudes

Infectious diseases of poverty (IDoP) affect disproportionately resource-limited and marginalized populations, resulting in spatial patterns of vulnerability across various geographical areas. Currently, no spatial indices exist to quantify vulnerability to IDoP at a fine geographical level within countries, such as municipalities or provinces. Without such an index, policymakers cannot effectively allocate resources or target interventions in the most vulnerable areas. This protocol aims to specify a methodological approach to measure spatial variation in vulnerability to IDoP. We will evaluate this methodological approach using surveillance and seroprevalence data from the Dominican Republic (DR) as part of a broader effort to develop a regional index for the Caribbean region. The study will consist of three main components. The first component involves identifying the relevant factors associated with IDoP in the Caribbean region through a scoping review, supplemented by expert-elicited opinion. The second component will apply a Fuzzy Analytic Hierarchy Process to weigh the aforementioned factors and develop a spatial composite index, using open data and available national surveys in the DR. In the final component, we will evaluate and validate the index by analysing the prevalence of at least three IDoPs at a fine-grained municipal level in the DR, using seroprevalence data from a 2021 national field study and other national surveillance programs. The spatial vulnerability index framework developed in this study will assess the degree of vulnerability to IDoP across different geographical scales, depending on data availability in each country.

Japanese Encephalitis Virus (JEV) transmission in temperate Australia has underscored a critical need to characterise transmission pathways and identify probable hosts of infection within the country. This systematic review consolidates existing research on the vertebrate hosts of JEV that are known to exist in Australia. Specifically, we aim to identify probable species for JEV transmission, their potential role as either a spillover or maintenance host and identify critical knowledge gaps. Data were extracted from studies involving experimental infection, seroprevalence, and virus isolation and were available for 22 vertebrate species known to reside in Australia. A host competence score was calculated to assess the potential for a given species to infect JEV vectors and to quantity their possible role in JEV transmission. Based on the host competence score and ecology of each species, we find ardeid birds, feral pigs, and flying foxes have potential as maintenance hosts for JEV in the Australian context. We also note that brushtail possums and domestic pigs have potential as spillover hosts under certain outbreak conditions. However, evidence to confirm these roles in localized transmission or outbreaks is sparse, emphasizing the need for further targeted research. This review provides a foundation for future investigations into JEV transmission in Australia, advocating for enhanced surveillance and standardized research methodologies to better understand and mitigate the virus’s impact.