Infectious Disease

Deer Tick, Lyme Disease VectorInfectious diseases like malaria, schistosomiasis, dengue fever, and zika virus are responsible for large burdens of disease globally and are highly sensitive to changes in environmental conditions, including temperature, soil moisture and precipitation patterns, deforestation, dams and irrigation projects, and others. It’s an urgent priority to better understand how land management practices alter the risk of these diseases in different settings and what types of interventions can reduce exposure to these diseases. Most emerging diseases globally are zoonotic diseases (with both human and animal hosts), and clearer understanding of anthropogenic influences on the emergence of zoonotic diseases (like HIV and Ebola) is another priority in planetary health research. Given the implications for food security and livelihoods, as well as for the state of global biodiversity, animal disease is also an important subtheme of disease ecology in the planetary health research context.

Learning Objectives

  • L1: Understand the environment-host-pathogen disease triangle and provide examples.
  • L2: Explain how environmental change can change the incidence, prevalence, geographical distribution, and/or severity of infectious diseases.
  • L3: Describe the criteria for an infectious disease hot spot and explain their characteristics with regard to environmental change.
  • L4: Recognize the interface between human and animal health in the contexts of environmental change and infectious diseases.


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Sorensen CJ, Borbor-Cordova MJ, Calvello-Hynes E, Diaz A, Lemery J, Stewart-Ibarra AM. Climate Variability, Vulnerability, and Natural Disasters: A Case Study of Zika Virus in Manabi, Ecuador Following the 2016 Earthquake . GeoHealth [Internet]. 2017;1 (8) :298–304. Publisher's VersionAbstract

Climate change presents complex and wide-reaching threats to human health. A variable and changing climate can amplify and unmask ecological and socio-political weaknesses and increase the risk of adverse health outcomes in socially vulnerable regions. When natural disasters occur in such areas, underlying climatic conditions may amplify the public health crisis. We describe an emerging epidemic of Zika virus (ZIKV) in Ecuador following the 2016 earthquake, which coincided with an exceptionally strong El Niño event. We hypothesize that the trigger of a natural disaster during anomalous climate conditions and underlying social vulnerabilities were force multipliers contributing to a dramatic increase in ZIKV cases postearthquake.

Muhling BA, Jacobs J, Stock CA, Gaitan CF, Saba VS. Projections of the future occurrence, distribution, and seasonality of three Vibrio species in the Chesapeake Bay under a high-emission climate change scenario . GeoHealth [Internet]. 2017;1 (7). Publisher's VersionAbstract
Illness caused by pathogenic strains of Vibrio bacteria incurs significant economic and health care costs in many areas around the world. In the Chesapeake Bay, the two most problematic species are V. vulnificus and V. parahaemolyticus, which cause infection both from exposure to contaminated water and consumption of contaminated seafood. We used existing Vibrio habitat models, four global climate models, and a recently developed statistical downscaling framework to project the spatiotemporal probability of occurrence of V. vulnificus and V. cholerae in the estuarine environment, and the mean concentration of V. parahaemolyticus in oysters in the Chesapeake Bay by the end of the 21st century. Results showed substantial future increases in season length and spatial habitat for V. vulnificus and V. parahaemolyticus, while projected increase in V. cholerae habitat was less marked and more spatially heterogeneous. Our findings underscore the need for spatially variable inputs into models of climate impacts on Vibrios in estuarine environments. Overall, economic costs associated with Vibrios in the Chesapeake Bay, such as incidence of illness and management measures on the shellfish industry, may increase under climate change, with implications for recreational and commercial uses of the ecosystem.
Herrera D, Ellis A, Fisher B, Golden CD, Johnson K, Mulligan M, Pfaff A, Treuer T, Ricketts TH. Upstream watershed condition predicts rural children’s health across 35 developing countries . Nature Communications [Internet]. 2017. Publisher's VersionAbstract

Diarrheal disease (DD) due to contaminated water is a major cause of child mortality globally. Forests and wetlands can provide ecosystem services that help maintain water quality. To understand the connections between land cover and childhood DD, we compiled a database of 293,362 children in 35 countries with information on health, socioeconomic factors, climate, and watershed condition. Using hierarchical models, here we find that higher upstream tree cover is associated with lower probability of DD downstream. This effect is significant for rural households but not for urban households, suggesting differing dependence on watershed conditions. In rural areas, the effect of a 30% increase in upstream tree cover is similar to the effect of improved sanitation, but smaller than the effect of improved water source, wealth or education. We conclude that maintaining natural capital within watersheds can be an important public health investment, especially for populations with low levels of built capital.

Pearce T, Currenti R, Mateiwai A, Doran B. Adaptation to climate change and freshwater resources in Vusama village, Viti Levu, Fiji . Regional Environmental Change [Internet]. 2017. Publisher's VersionAbstract

Changing precipitation patterns including more intense and prolonged dry periods have become a growing concern for people living in the Pacific Island region. People in the region are particularly sensitive to these changes given their resource-based livelihoods and high dependence on rainfall for their freshwater needs. Despite this, little attention has been given to understanding the implications of climatic changes for people and their capacity to manage these changes. This paper assesses human vulnerability to climate change (as it relates to fresh water resources) in Vusama, an iTaukei village in southwest Viti Levu, Fiji in the context of recent social and ecological changes. An analysis of data collected using a vulnerability approach that included semi-structured interviews, participant observation and analysis of secondary sources reveal that climate change together with behavioural changes are negatively affecting availability and access to clean freshwater, with implications for household economies, food security and human health. In particular, prolonged drought and changing seasonal patterns, together with people’s increasing reliance on a village borehole in lieu of family wells have resulted in a freshwater crisis. People are coping by using earnings from wage employment and harvesting and selling seafood to buy water and vegetables, rationing freshwater and depending on extended social networks for fresh produce. Current responses are reactive and short-term. Longer-term adaptation strategies are needed that consider expected future climate change and broader human development goals.

Pattanayak SK, Kramer RA, Vincent JR. Ecosystem change and human health: implementation economics and policy. Philosophical Transactions of the Royal Society B [Internet]. 2017;372 (1722). Publisher's VersionAbstract

Several recent initiatives such as Planetary Health, EcoHealth and One Health claim that human health depends on flourishing natural ecosystems. However, little has been said about the operational and implementation challenges of health-oriented conservation actions on the ground. We contend that ecological–epidemiological research must be complemented by a form of implementation science that examines: (i) the links between specific conservation actions and the resulting ecological changes, and (ii) how this ecological change impacts human health and well-being, when human behaviours are considered. Drawing on the policy evaluation tradition in public economics, first, we present three examples of recent social science research on conservation interventions that affect human health. These examples are from low- and middle-income countries in the tropics and subtropics. Second, drawing on these examples, we present three propositions related to impact evaluation and non-market valuation that can help guide future multidisciplinary research on conservation and human health. Research guided by these propositions will allow stakeholders to determine how ecosystem-mediated strategies for health promotion compare with more conventional biomedical prevention and treatment strategies for safeguarding health.


Adger WN, W.Arnell N. Successful adaptation to climate change across scales. Global Environmental Change [Internet]. 2005;15 (2). Publisher's VersionAbstract

Climate change impacts and responses are presently observed in physical and ecological systems. Adaptation to these impacts is increasingly being observed in both physical and ecological systems as well as in human adjustments to resource availability and risk at different spatial and societal scales. We review the nature of adaptation and the implications of different spatial scales for these processes. We outline a set of normative evaluative criteria for judging the success of adaptations at different scales. We argue that elements of effectiveness, efficiency, equity and legitimacy are important in judging success in terms of the sustainability of development pathways into an uncertain future. We further argue that each of these elements of decision-making is implicit within presently formulated scenarios of socio-economic futures of both emission trajectories and adaptation, though with different weighting. The process by which adaptations are to be judged at different scales will involve new and challenging institutional processes.

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