Climate change and infectious diseases in North America: the road ahead

Abstract

Global climate change is inevitable--the combustion of fossil fuels has resulted in a buildup of greenhouse gases within the atmosphere, causing unprecedented changes to the earth's climate. The Fourth Assessment Report of the Intergovernmental Panel on Climate Change suggests that North America will experience marked changes in weather patterns in coming decades, including warmer temperatures and increased rainfall, summertime droughts and extreme weather events (e.g., tornadoes and hurricanes). Although these events may have direct consequences for health (e.g., injuries and displacement of populations due to thermal stress), they are also likely to cause important changes in the incidence and distribution of infectious diseases, including vector-borne and zoonotic diseases, water-and food-borne diseases and diseases with environmental reservoirs (e.g., endemic fungal diseases). Changes in weather patterns and ecosystems, and health consequences of climate change will probably be most severe in far northern regions (e.g., the Arctic). We provide an overview of the expected nature and direction of such changes, which pose current and future challenges to health care providers and public health agencies.

Figure 1: Trends in mean global temperatures since the mid-19th century. Coloured lines represent the linear trends over various time periods. Shorter (more recent time periods) lines have steeper slopes, indicating an accelerating warming trend for the planet. Reproduced, with permission, from reference 2. Copyright 2007 Cambridge University Press.

Figure 2: Upper temperature limits for Ixodes scapularis establishment in Canada, based on mathematical models. The graph shows the current upper geographic limits and projected limits for the 2020s, 2050s and 2080s, assuming continuous population growth, regionally oriented economic development and no reduction in greenhouse gas emissions. Upper and lower model-derived confidence limits are mapped as coloured lines around the black lines. Modified, with permission, from Elsevier (Int J Parasitol 2006;36: 63–70).

Figure 3: Association between precipitation and water-borne disease outbreaks. The graph shows the relation between unusually heavy rainfall and the number of confirmed cases of verotoxigenic Escherichia coli infection that occurred during a massive enteric disease outbreak in Walkerton, Ontario, in May 2000. The incubation period for verotoxigenic E. coli is usually 3–4 days, which is consistent with the lag between extreme precipitation events and surges in the number of cases. The figure is based on data published by Auld et al and data published in Report of the Walkerton Inquiry: the events of May 2000 and related issues. Part one.