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The impacts of global environmental change have precipitated numerous approaches that connect the health of ecosystems, non-human organisms and humans. However, the proliferation of approaches can lead to confusion due to overlaps in terminology, ideas and foci. Recognising the need for clarity, this paper provides a guide to seven field developments in environmental public health research and practice: occupational and environmental health; political ecology of health; environmental justice; ecohealth; One Health; ecological public health; and planetary health. Field developments are defined in terms of their uniqueness from one another, are historically situated, and core texts or journals are highlighted. The paper ends by discussing some of the intersecting features across field developments, and considers opportunities created through such convergence. This field guide will be useful for those seeking to build a next generation of integrative research, policy, education and action that is equipped to respond to current health and sustainability challenges.

Typhoid fever is endemic in Fiji, with high reported annual incidence. We sought to identify the sources and modes of transmission of typhoid fever in Fiji with the aim to inform disease control. We identified and surveyed patients with blood culture-confirmed typhoid fever from January 2014 through January 2017. For each typhoid fever case we matched two controls by age interval, gender, ethnicity, and residential area. Univariable and multivariable analysis were used to evaluate associations between exposures and risk for typhoid fever. We enrolled 175 patients with typhoid fever and 349 controls. Of the cases, the median (range) age was 29 (2-67) years, 86 (49%) were male, and 84 (48%) lived in a rural area. On multivariable analysis, interrupted water availability (odds ratio [OR] = 2.17; 95% confidence interval [CI] 1.18-4.00), drinking surface water in the last 2 weeks (OR = 3.61; 95% CI 1.44-9.06), eating unwashed produce (OR = 2.69; 95% CI 1.48-4.91), and having an unimproved or damaged sanitation facility (OR = 4.30; 95% CI 1.14-16.21) were significantly associated with typhoid fever. Frequent handwashing after defecating (OR = 0.57; 95% CI 0.35-0.93) and using soap for handwashing (OR = 0.61; 95% CI 0.37-0.95) were independently associated with a lower odds of typhoid fever. Poor sanitation facilities appear to be a major source of Salmonella Typhi in Fiji, with transmission by drinking contaminated surface water and consuming unwashed produce. Improved sanitation facilities and protection of surface water sources and produce from contamination by human feces are likely to contribute to typhoid control in Fiji.

Covering over 71% of the Earth's surface, the oceans serve as an essential carbon sink.1 Oceans also regulate climate-associated human health risks between land and sea, ranging from direct injuries and deaths associated with extreme weather events, to negative effects on food and nutrition security, and even chronic diseases (eg, cancer) from ocean pollution.2 Furthermore, oceans are a source of joy, recreation, spiritual and mental wellbeing, healing, and entertainment, enriching human lives beyond their basic needs. Other coastal communities around the world, as well as land-locked states, are increasingly affected as the effects of climate on global oceans become more severe because of the ocean's increasing inability to accommodate the carbon and heat generated by human activities. Practically, this inclusion can be achieved by integrating multiple knowledge systems into the coproduction of impact assessments and decision-making processes.12 Moreover, ensuring that all the ocean's stakeholders share the benefits of marine resources equitably (including from sustainable fishing and bioprospecting) will incentivise their active participation, contributing to both conservation goals and socioeconomic wellbeing.12 The wellbeing of Indigenous people and local communities also stands to benefit from the application of area-based management measures (eg, marine protected areas) that assist in the preservation of cultural history and practice.

The human microbiome, described as an accessory organ because of the crucial functions it provides, is composed of species that are uniquely found in humans 1 , 2 . Yet, surprisingly little is known about the impact of routine interpersonal contacts in shaping microbiome composition. In a relatively ‘closed’ cohort of 287 people from the Fiji Islands, where common barriers to bacterial transmission are absent, we examine putative bacterial transmission in individuals’ gut and oral microbiomes using strain-level data from both core single-nucleotide polymorphisms and flexible genomic regions. We find a weak signal of transmission, defined by the inferred sharing of genotypes, across many organisms that, in aggregate, reveals strong transmission patterns, most notably within households and between spouses. We were unable to determine the directionality of transmission nor whether it was direct. We further find that women harbour strains more closely related to those harboured by their familial and social contacts than men, and that transmission patterns of oral-associated and gut-associated microbiota need not be the same. Using strain-level data alone, we are able to confidently predict a subset of spouses, highlighting the role of shared susceptibilities, behaviours or social interactions that distinguish specific links in the social network. Strain-level analysis of gut and oral microbiomes from individuals living in the Fiji Islands identified shared genomes particularly within households, indicating potential microbial transmission within social networks.

Proximal characteristics and conditions in the residential setting deserve greater attention for their potential to influence typhoid transmission. Using a case-control design in Central Division, Republic of Fiji, we examined bacterial (coliform and Escherichia coli) contamination and chemical composition of water and soil as potential vehicles of exposure to Salmonella Typhi, combining observational analysis of residential living conditions, geospatial analysis of household locations, and factor analysis to explore multivariate associations with the risk of developing typhoid fever. Factors positively associated with typhoid infection related to drainage [phosphate (OR 4.235, p = 0.042) and E. coli concentrations (OR 2.248, p = 0.029) in toilet drainage soil, housing [external condition (OR 3.712, p < 0.001)], drinking water contamination (OR 2.732, p = 0.003) and sanitary condition (OR 1.973, p = 0.031). These five factors explained 42.5% of the cumulative variance and were significant in predicting typhoid infection. Our results support the hypothesis that a combination of spatial and biophysical attributes of the residential setting influence the probability of typhoid transmission; in this study, factors associated with poor drainage, flooding, and sanitary condition increase local exposure to contaminated water and soil, and thereby infection. These findings extend testing of causal assumptions beyond the immediate domestic domain, enhance the scope of traditional case control epidemiology and allow greater specificity of interventions at the scale of the residential setting.

We surveyed freshwater ichthyofaunal communities in streams of Vanua Levu, Fiji, under a range of land cover to assess differential, seasonal effects on fish abundance and diversity. We collected fish from 32 families, 19 genera and 87 species, representing approximately 50% of the known Fijian freshwater and estuarine fish fauna. Position in reach was the strongest overall factor influencing fish abundance and diversity, particularly in the larger, steeper catchments. However, fish communities exhibited strong seasonal specificity with over half (55%) of species observed in only one season. There were greater numbers of estuarine and marine migrants and fishes with poor swimming ability in the dry season, with more schooling species, large predators and fish that prefer muddy benthos in the wet. In the more pristine catchments of Kubulau District, higher species abundance and diversity were observed in the wet season and were associated with significantly greater flow, pH and dissolved oxygen. We observed the opposite pattern for fish diversity and abundance from the more degraded catchments of Macuata Province. These results suggest that the wet season is having a net positive effect on habitable space for fishes in Kubulau and a net negative effect in Macuata, as species may be lost due to increased runoff from heavily cleared and cultivated catchments. Integrated water resource management across the full range of habitats utilized by Fiji’s freshwater fishes is recommended in order to maintain species diversity and abundance.

We propose a new approach for island-wide planning and implementation of ecosystem management in the Pacific, recognizing a lack of replicability, sustainability and cost-effectiveness in other approaches. ?Integrated island management' (IIM) operates through coordinated networks of institutions and communities focused on sustainable and adaptive management of natural resources. IIM enables simultaneous and cost-effective achievement of ecosystem-based management, climate change adaptation and disaster risk reduction while conserving biodiversity, maintaining ecosystem services and securing human health and well-being. We present ten guiding principles for IIM, and then use these to evaluate 36 case studies from the Pacific islands. Most case studies were pilot or demonstration projects with little evidence of planning to ensure long-term financial and human capacity needs were sustained, beyond the life of the projects, or could be replicated at significant scales. Management outcomes in the Pacific will be enhanced by: (1) building on foundations of customary management practice and social networks; (2) working holistically across relevant ecological and governance scales, through coordinated but decentralized and nested institutions; (3) empowering local communities to participate in integrated planning and implementation; and (4) embedding IIM practice into national systems for long-term sustainability and replication. These also ultimately depend on the context and externalities, beyond the control of practitioners. Cost-effectiveness and appropriateness are also critical for successful IIM in the Pacific islands but ultimately there is little alternative for effective biodiversity conservation.

To tackle these compounding challenges and take advantage of all that the 21st century has to offer, it will be necessary to draw on the power, ideas, and leadership capabilities of young people to reimagine and recreate a healthier, fairer, and just planet. Investments across adolescence—ie, the period between age 10 years and 24 years—will reap a triple dividend, with benefits for young people today, for the adults they will become, and for the next generation of children whom they will parent. Strengthen community systems that promote mental health and wellbeing Develop innovative approaches to address complex and emerging health threats in partnership with adolescents Against these advances, strikingly little progress has been made in reducing adolescent non-communicable diseases in every region of the world, with rises globally in obesity-related diseases and mental disorders in young people.

Watersheds offer opportunities for place-based interventions to transform systems health via preventative versus reactive approaches to management that achieve multiple co-benefits for public and environmental health. The Watershed Interventions for Systems Health in Fiji (WISH Fiji) project embraced participatory knowledge co-production and action-oriented research to identify risks to public and ecosystem health, prioritize interventions to address risks, and monitor responses of the system to interventions. We used screening filters and local knowledge to collaboratively identify five watersheds for action with high prior incidence of water-related diseases (Fiji’s “three plagues” of leptospirosis, typhoid and dengue) and high risk to downstream environmental health. We reviewed literature to identify disease risk factors, evaluated overlaps with risks for downstream environmental impact, and designed 13 instruments to collect information about baseline risk. Following consultations to obtain free, prior and informed consent, we enrolled 311 households across 29 communities. We synthesized data to identify key risks at the household, community, and landscape level, which were communicated to community water and resource management committees and government leaders as part of developing water and sanitation safety plans for each community. Local committees identified 339 priority risk reduction actions across nine main categories: animal management; drainage; health systems surveillance; hygiene; integrated planning; land use management; sanitation systems; waste management; and water systems. As of October 2022, 154 interventions were implemented in the five watersheds across different risk categories and scales. While we can track changes to factors that reduce risk of water-related disease and improve environmental health, direct evaluation of impacts to public health is limited due to poor geolocation of case records. The WISH Fiji project is a model of cross-sectoral coordination that efficiently progresses multiple Sustainable Development Goals, but scaling requires sustained investment in interventions to realize full benefits, particularly for nature-based solutions that exhibit lagged responses.

The human microbiome, described as an accessory organ because of the crucial functions it provides, is composed of species that are uniquely found in humans. Yet, surprisingly little is known about the impact of routine interpersonal contacts in shaping microbiome composition. In a relatively 'closed' cohort of 287 people from the Fiji Islands, where common barriers to bacterial transmission are absent, we examine putative bacterial transmission in individuals' gut and oral microbiomes using strain-level data from both core SNPs and flexible genomic regions. We find a weak signal of transmission, defined by the inferred sharing of genotypes, across many organisms that, in aggregate, reveals strong transmission patterns, most notably within households and between spouses. We find that women harbor strains more closely related to those harbored by their familial and social contacts than men; and that transmission patterns of oral- and gut-associated microbiota need not be the same. Using strain-level data alone, we are able to confidently predict a subset of spouses, highlighting the role of shared susceptibilities, behaviors or social interactions that distinguish specific links in the social network.