Infectious disease incidence will change as a result of global climate change. This is considered an indirect (McMichael, 2013) or secondary (Butler and Harley, 2010) effect. The elucidation of causal links between global climate change and infectious disease incidence is challenging, particularly because of interaction with other risk determinants including urbanisation, environmental changes, travel, ecology, human demographics, and societal factors.
The involvement of other animals in infectious disease transmission (vertebrate reservoir hosts, intermediate hosts for parasites, and arthropod vectors) significantly influences climate sensitivity. While climatic influences are recognised for pathogens that are not zoonotic, vector-borne, or transmitted via intermediate hosts, salmonellosis and influenza for example, considerable research focus has been on vector-borne and zoonotic diseases. Indeed, changes in vector or disease distribution are considered possible early indicators of the health effects of climate change – tick-borne encephalitis in Sweden, the Lyme disease vector in Canada, and malaria in the Kenyan highlands are examples (Harley, Swaminathan et al., 2011).
Policy relevant Australian research on infectious diseases and climate change should focus on burden, projection of incidence changes, and adaptation (Harley, Bi et al., 2011). In relation to the first of these, realistic assessments of impact are needed to determine the importance of infectious diseases relative to one another, but also in the context of other health system challenges. It is crucial to consider carefully the appropriate methods for adaptation research. Economics, particularly in relation to opportunity costs and unintended consequences of adaptation, should be given weight.
Questions to get you thinking
Butler, CD and Harley, D, 2010. Primary, secondary and tertiary effects of eco-climatic change: the medical response. Postgraduate Medical Journal 86: 230–4.
Harley, D, Bi, P, Hall, G, Swaminathan, A, Tong, S and Williams, C, 2011. Climate change and infectious diseases in Australia: future prospects, adaptation options and research priorities. Asia-Pacific Journal of Public Health: 23 (Supp. 2): 54S–66S.
Harley, D, Swaminathan, A and McMichael, AJ, 2011. Climate change and the geographical distribution of infectious diseases. In Petersen, E, Chen, LH and Schlagenhauf, P (eds), Infectious diseases: a geographic guide, Wiley Blackwell, Oxford.
McMichael, AJ, 2013. Globalization, climate change, and human health New England Journal of Medicine 368: 1335–43.
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