Global Climate Change and Extreme Weather Events Understanding the Contributions to Infectious Disease Emergence: Workshop Summary (2008) / Chapter Skim
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1 Climate Change Challenges
1 Climate Change Challenges
Pages 54-103
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From page 54... ...
Several examples illustrate how variations in climate -- in the form of floods, droughts, and other extreme weather events -- influence the range and transmission dynamics of infectious diseases, and therefore suggest potential effects of climate change. Yet, as Haines observes, "in the case of infectious 54
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From page 55... ...
The first manuscript is an essay, originally published in the New England Journal of Medicine in October 2005 -- weeks after Hurricane Katrina devastated the Gulf Coast -- that focuses on the wide-ranging health effects of extreme weather. The second, an excerpt from the report Climate Change Futures: Health, Ecological and Economic Dimensions (Center for Health and the Global Environment, 2005)
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From page 56... ...
, the composite pattern warrants further attention. This may take the form of analyzing attribution probabilities for anomalous events; for example, such an assessment indicates that global warming increased the likelihood of the European heat wave of 2003 two- to fourfold (Stott et al., 2004)
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From page 57... ...
To support this contention, he presents detailed analyses of the transmission dynamics of two infectious diseases: influenza and dengue fever. These studies reveal that oscillations in disease incidence occur in the absence of seasonal transmission effects; if these patterns coincide with seasonal variation, small changes in transmissibility may, under some circumstances, produce considerable variability from year to year in epidemic disease occurrence (Dushoff et al., 2004)
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From page 58... ...
Regional-scale changes are outlined in Box 1-1. Climate Variability, Climate Change, and Health It has been known for thousands of years, at least since the time of Hippocrates, that climatic variations can influence health, particularly through changes in temperature and precipitation, as well as extreme weather events.
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global average sea level rise from tide gauge (blue) and satellite (red)
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; migration of populations, which may result in the exposure of nonimmune populations to infectious diseases; and changes in the performance of disease surveillance systems over time. Some diseases, such as malaria, exhibit differences in
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From page 61... ...
Improvements in public health infrastructure leading to improved adaptation to climate change could, in the future, attenuate relationships between the changing climate and health outcomes. Climate change is likely to be a longterm process that will evolve over decades and centuries while our understanding of the linkages between climate and health is based largely on studies of shortterm variability.
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A summary of the pathways through which climate change may affect human health including infectious diseases is shown in Figure 1-3. Rainfall, Temperature, and Disease Water-related diseases include water-borne diseases due to ingestion of pathogens in contaminated water and water-washed diseases as a result of poor hygiene.
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Adverse Health Effects Heat-Related Illnesses and Deaths Extreme Weather Related Health Effects Changes in Intermediate Factors Regional and Local Weather Change Air Pollution Concentration Air Pollution Natural and Climate Variability and Distribution Related Health Effects Human Influences and Change Extreme Weather on Climate Temperature Pollen Production Allergic Diseases Precipitation Infectious Diseases Water- and Microbial Contamination Food-Borne Diseases and Transmission Vector- and Rodent-Borne Diseases Crop Yield Malnutrition Mitigation Policies Storm Surge-Related Change in Coastal Flooding Drowning and Injuries Sea Level Coastal Aquifer Salinity Health Problems of Displaced Populations Moderating Influences and Adaptation Measures Mitigation Policies for Reduction Moderating Influences Adaptation Measures of Greenhouse Gas Emissions Population Density and Growth Vaccination Programs Energy Efficiency Level of Technological Development Disease Surveillance Use of Renewable Energy Sources Standard of Living and Local Environmental Condition Protective Technologies Forest Preservation Preexisting Health Status Weather Forecasting and Warning Systems Quality and Access to Health Care Emergency Management and Disaster Preparedness Public Health Infrastructure Public Health Education and Prevention Legislation and Administration FIGURE 1-3 Pathways by which climate change may affect human health, including infectious diseases. SOURCE: Reprinted from Haines and Patz (2004)
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From page 64... ...
with climatic changes in Australia, Indonesia, the Pacific highlands, and East Africa, as well as parts of Latin and North America, the El Niño cycle is usually between 3 and 7 years. The El Niño (warm event)
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From page 65... ...
There also needs to be a plausible biological relationship between the health outcome in question and climate variability, and appropriate statistical analysis is required, taking into account autocorrelation and using, where available, long time series of data over decadal periods. There have also been numerous case reports of associations of disease outbreaks with single ENSO events, although these provide less compelling evidence of association.
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From page 66... ...
. Likewise in the case of Rift Valley fever in East Africa, there is good evidence that epidemics in the dry grasslands are triggered by heavy rainfall events, but there is no association between this disease in Kenya and the ENSO index (Linthicum et al., 1999)
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Salinization of freshwater aquifers may occur as a result of incursion of seawater. Even in industrialized countries, densely populated urban areas are at risk from sea level rise, as shown by the impact of Hurricane Katrina on New Orleans.
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Food shortages Impaired immune system Increased risk of infections Malnutrition Population movement Socioeconomic turmoil Interruption of health services Forest fires Respiratory ailments Scarcity of potable water Diarrheal diseases Inadequate handwashing FIGURE 1-6 Potential health effects of drought in developing countries. SOURCE: Adapted from Kovats et al.
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From page 69... ...
. Both fatalities and direct economic losses of national per capita income from natural disasters are higher by orders of magnitude in low- and middle-income countries compared to high-income countries (Linnerooth-Bayer et al., 2005)
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. Other authors have shown that climatic factors play a role in malaria epidemics in the East African highlands.
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From page 71... ...
. Estimating the Impact of Climate Change on Infectious Diseases A growing number of studies that have modeled projected impacts of climate change on health have been reviewed by the IPCC (IPCC, 2007b)
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The threat of climate change has resulted in increased interest in climatebased early warning health systems for heat waves and climate-sensitive diseases. Early warning systems must be integrated into local health systems if they are to have an impact.
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From page 73... ...
. Although most renewable energy technologies can provide near-term benefits for health, for example by reducing exposure to air pollution, as well as mitigating greenhouse gas emissions, it is important that health impact assessments are undertaken.
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Then came Hurricane Katrina, gathering steam from the heated Gulf of Mexico and causing devastation in coastal communities. These sorts of extreme weather events reflect massive and ongoing changes in our climate to which biologic systems on all continents are reacting.
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Given the current rate of carbon dioxide buildup and the projected degree of global warming, we are entering uncharted seas. Hassol SJ.
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Meanwhile, in the past three decades, widening social inequities and changes in biodiversity -- which alter the balance among predators, competitors, and prey that help keep pests and pathogens in check -- have apparently contributed to the resurgence of infectious diseases. Global warming and wider fluctuations in weather help to spread these diseases: temperature constrains the range of microbes and vectors, and weather affects the timing and intensity of disease outbreaks.
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From page 77... ...
In highland regions, as permafrost thaws and glaciers retreat, mosquitoes and plant communities are migrating to higher ground. The increased weather variability that accompanies climate instability contributed to the emergence of both the hantavirus pulmonary syndrome and West Nile virus in the United States.
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When small Appears to be low-res -- keep the meltwater seeps through cracks in the ice sheet, it may accelerate melting and allow ice to slide more easily over bedrock, speeding its movement to the sea. In addition to contributing to a rising sea level, this process adds freshwater to the ocean, with potential effects on ocean circulation and regional climate.
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All in all, it would appear that we may be underestimating the breadth of biologic responses to changes in climate. Treating climate-related ills will require preparation, and early-warning systems forecasting extreme weather can help to reduce casualties and curtail the spread of disease.
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The risks to oil production compound the threats to the electricity grid from heat waves and the instabilities of pipelines grounded in thawing tundra. At the same time, recovery, adaptation and prevention open the door to enormous opportunities.
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from August 25-27, 2005, and the growing breadth of Hurricane Katrina as it passed over the warm Gulf of Mexico. Yellow, orange and red areas are at or above 82°F (27.7°C)
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"Climate Change Futures" focuses on health. The underlying premise of this report is that climate change will affect the health of humans as well as the ecosystems and species on which we depend, and that these health impacts will have economic consequences.
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Moreover, in the past decade, an increasing proportion of extreme weather events have been occurring in developed nations (Europe, Japan and the US) (see chart below)
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84 Extreme Weather Events by Region 500 South America Oceania 400 Europe Africa 300 North America (including Caribbean, Central America) Asia (including Russia)
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2. Extreme weather events create conditions conducive to disease outbreaks.
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Threshold-crossing events in both terrestrial and marine systems would severely compromise resources and ecological functions, with multiple consequences for the species that depend upon them. For example: • Repeated heat waves on the order of the 2003 and 2005 summers could severely harm populations, kill livestock, wilt crops, melt glaciers and spread wildfires.
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Many factors, including land-use changes and growing poverty, have contributed to the increase. Our examination of malaria, West Nile virus and Lyme disease explores the role of warming and weather extremes in
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Warming affects its range, and extreme weather events can precipitate large outbreaks. This study documents the fivefold increase in illness following a 6-week flood in Mozambique, explores the surprising role of drought in northeast Brazil, and projects changes for malaria in the highlands of Zimbabwe.
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From page 89... ...
Extreme Weather Events • Temperature: Heat waves are becoming more common and more intense throughout the world. This study explores the multiple impacts of the highly anomalous 2003 summer heat wave in Europe and the potential impact of such "outlier" events elsewhere for human health, forests, agricultural yields, mountain glaciers and utility grids.
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From page 90... ...
. This expert committee concluded that although it is clear that weather fluctuations and seasonal-to-interannual climate variability influence many infectious diseases, published observational and modeling studies must be interpreted cautiously, and consequently the exact future impacts of global climate change remain uncertain.
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From page 91... ...
High confidence negative impacts of climate change on human health included more malnutrition; more deaths, injuries, and diseases from extreme weather events; and more cardiorespiratory diseases from the deterioration of air quality. However, findings related to infectious diseases were careful and circumscribed.
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For any given geographic locale, the net effects on human health may be negative, neutral, or positive, depending on local infectious disease circumstances. Predic TABLE 1-1 Examples of Environmental Factors Known to Be Strongly Associated with Certain Specific Infectious Diseases Environmental Condition Disease Favored Evidence Warm Malaria, dengue Primarily tropical distribution, seasonal transmission pattern Cold Influenza Seasonal transmission pattern Dry Meningococcal meningitis, Associated with arid conditions, dust storms coccidioidomycosis Wet Cryptosporidiosis, Associated with flooding Rift Valley fever SOURCE: NRC (2001)
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From page 93... ...
Under conditions of high temperature or high relative humidity, none of the four downwind guinea pigs breathing infectious air became infected. In contrast, under conditions of low temperature and/or low relative humidity, four of four downwind animals invariably became infected.
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. low relative humidity increased transmission, the temperature effect mediated by increased virus shedding and the relative humidity effect probably by bioaerosol formation of droplet nuclei.
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From page 95... ...
. If natural influenza systems follow the same behaviors as this model system, then it may prove difficult indeed to measure seasonal changes in disease incidence as a function of seasonal changes in the transmission parameter β.
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From page 96... ...
. Working with our colleagues at the Thailand Ministry of Public Health, we reviewed epidemiological records over many years, entered them into digital format, and applied decomposition methods.
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From page 97... ...
to analyze 15 consecutive years of the incidence of dengue hemorrhagic fever in Bangkok. A major feature of the Empirical Mode Decomposition is that the method identifies component "modes" of differing frequency, from fast to slow, that together contribute to the full tracing of the epidemic time series.
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From page 98... ...
Conclusions In this paper, I have argued that our current understanding of the relationships between climate and weather and epidemic infectious diseases is insufficient to make quantitative predictions about future threats posed by infectious diseases under various global climate change scenarios. Nonetheless, I am confident that new state-of-the-art methods, including computational tools, are now available to apply to these difficult scientific problems.
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From page 99... ...
1994. Vulnerability of Bangladesh to climate change and sea level rise: con cepts and tools for calculating risk in integrated coastal zone management.
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From page 100... ...
Technical summary. Contribution of Working Group II to the fourth assessment report of the Intergovernmental Panel on Climate Change, edited by M
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From page 101... ...
2000. The potential health impacts of climate variability and change for the United States: executive summary of the report of the health sector of the U.S.
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2004. Association between climate variability and malaria epidemics in the east African highlands.
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1998. The empirical mode decomposition and the Hilbert spectrum for nonlin ear and non-stationary time series analysis.
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