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Environment, Society, Climate and Health: Analysis, Understanding and Prediction Mark L. Wilson Department of Epidemiology and Global Health Program School of Public Health The University of Michigan Colloquium on Climate and Health NCAR Boulder, Colorado 23 July, 2004 Outline 1. Introduction: Infectious Disease Epidemiology 2. Patterns of Environmental Influences 3. Climate as an Environmental Driver 4. Examples from our research 5. Discussion of examples from your research/interests Climate Variability vs. Climate Change • Climate Change: - persistent change or trend in mean atmospheric conditions - current changes unprecedented in human history • Climate Variability: - day-to-day (weather) or relatively short term (seasonal) changes in atmospheric conditions - effects on disease patterns most easily analyzed, and used in forecasts Classical Epidemiological Triad Environment Agent Host Environment* (biophysical, psycho-social, etc.) Agent Host (diverse exposures, including noncontagious ) (animal, plant, ultimately human) *CLIMATE is an Environmental Influence Environment Agent Host Examples Involving Infectious Diseases Environment longevity & infectivity outside host host distribution, abundance, infection e.g. cholera hantaviral disease hookworm schistosomiasis nutrition hygiene treatment housing e.g. TB, HIV/AIDS, diarrheal diseases, acute respiratory infections Agent Host tissue tropisms, pathogenicity, immune response, host specificity e.g. rabies, Lyme disease, malaria, cryptosporidiosi. But for ALL diseases, complex interactions occur... Environment Altered hygiene Improved irrigation Redesigned housing Better nutrition Agent Host Environment Agent transport to new areas New antibiotics, pesticides Labor actions affecting toxin exposure Agent Host Environment Agent Host Exposure probability, host immunity, support networks, availability of supportive care Examples of Environmental and Epidemiological Data • • • • • • • Climate patterns – variability… perhaps change… Land Use / Land Cover patterns Human case data (specific or syndromic) Vector abundance and pathogen infection Reservoir abundance / infection prevalence Environmental use and exposures Economic development, human demography, migration … more Each of these is historically changing in time and space Environmental Determinants of Human Disease Social and Economic Policies Institutions (including medical care) Living Conditions Social Relationships Individual Risk Factors Genetic/Constitutional Factors Pathophysiologic pathways Individual/Population Health Modified from Kaplan, 2002 Research Challenge – Analyze and understand interactions! Social and Economic Policies Institutions (including medical care) Living Conditions Social Relationships Individual Risk Factors Genetic/Constitutional Factors Pathophysiologic pathways Individual/Population Health Environmental Variable What is climate change? Climate variability? Unchanging Average, Unchanging Extremes Average Trend (solid line) Actual Measure (dashed line) Low Time Environmental Variable Unchanging Average, Increasing Extremes Average Trend (solid line) Actual Measure (dashed line) Low Time Environmental Variable Increasing Average, Unchanging Extremes Average Trend (solid line) Actual Measure (dashed line) Low Time Environmental Variable High Different Rates of Increasing Averages Average Trend (solid line) Actual Measure (dashed line) Low Time Environmental Variable Increasing Average, Greater Extremes Average Trend (solid line) Actual Measure (dashed line) Low Time Environmental Variable Increasing Rate of Increasing Average, Unchanging Extremes Average Trend (solid line) Actual Measure (dashed line) Low Time Environmental Variable Increasing Rate of Increasing Average, Greater Extremes Average Trend (solid line) Actual Measure (dashed line) Low Time Each of these climate change patterns may have different impacts on particular disease risks. Effects will depend on the ecology of transmission and the etiology and expression of disease. Each exposure type should be considered in context of: PERSON (age, behavior, gender, SES, etc.) TIME (year, season, adjacent periods, etc.) PLACE (geographic location, habitat, proximity, etc.) Most Epidemiological studies only superficially consider this for environmental (climatic) exposures: + PERSON most often involves standard descriptors that do not include "social" characteristics or other environmental exposures (e.g. climatic). TIME is rarely dynamic, considers only recent past, and climate pattern over long periods not always available. PLACE often ignored or not carefully evaluated (e.g. spatial autocorrelation, climate patterns in regions may be important Environment and Exposure Direct Exposure Indirect Exposure Environmental Exposures Source Source Vehicle Humans Humans Solar UV EM Radiation Tetanus Stream pollutants Air Particulates Legionella Anthroponotic Infections Humans Humans Vehicle Humans Vehicle Humans STDs Measles Hepatitis B Malaria Dengue Roundworm Zoonotic Infections Animals Animals Vehicle Animals Humans Vehicle Animals Anthrax Ebola (?) Humans Lyme Disease Hantaviral Disease Environment and Exposure Where might Climate Impact? Direct Exposure Indirect Exposure Environmental Exposures Source Source Vehicle Humans Solar UV EM Radiation Tetanus Humans Stream pollutants Air Particulates Legionella Environment and Exposure Where might Climate Impact? Direct Exposure Indirect Exposure Anthroponotic Infections Humans Humans Vehicle Humans STDs Measles Hepatitis B Vehicle Humans Malaria Dengue Roundworm Environment and Exposure Where might Climate Impact? Direct Exposure Indirect Exposure Zoonotic Infections Animals Animals Vehicle Animals Humans Vehicle Animals Anthrax Ebola (?) CJD Humans Lyme Disease Hantaviral Disease Most arboviral diseases Elements of Climate and Health Maximum Temperature Heat-related mortality Minimum Temperature Extreme Events Mean Temperature Air Pollution Rainfall Amount Vector-borne Diseases Rainfall Frequency Water-borne Diseases Rainfall Rate Agricultural Production What diseases are climate sensitive? Sensitivity High Moderate – Which are more sensitive???? • Less sensitive – What about less sensitive??? Low Sensitivity • More sensitive Lowest What diseases are climate sensitive? Sensitivity High Moderate – – – – – – – heat stress effects of storms air pollution effects asthma vector-borne diseases water-borne diseases food-borne diseases • Less sensitive – sexually transmitted diseases – violence – most cancers – atherosclerosis – tuberculosis – myocardial infarction Low Sensitivity • More sensitive Lowest Sexually transmitted Disease Heat stress Effects of Storms Water-borne disease Food-borne disease Asthma Atherosclerosis Vector-borne Disease Cancer (not skin) Myocardial Infarction Violence More Climate Sensitive Discussion… From YOUR EXPERIENCES or INTERESTS: • What diseases might have a climate link and what climate variables might impact on which diseases? • WHY? What are the biological or social pathways? • How would these be investigated/researched? • What additional information would you seek? • How would you integrate this into OTHER determinants of risk? • Could you forecast risk based on these analyses alone? • What other factors should be considered and why? Importance of temporally and spatially extensive data in analyzing and interpreting role of climate: • Climate change occurring over long time period • Climate variability change not easy to recognize without long-term observations • Time-space changes in disease patterns require accurate and consistent surveillance (often nonexistent, especially in developing countries) • Inference of climate-disease links limited without carefully considering time-space patterns Interpreting Spatial Patterns of Risk a b •Area of risk •Size of areas •Location and pattern •Inter-area distances •Connectivity among locations c d How can extensive time-space datasets help? Pattern of disease … or knowledge, SES, exposure, etc... T1 T2 T3 How can extensive time-space datasets help? Abundance / Prevalence How can extensive temporal datasets help? Time Abundance / Prevalence How can extensive temporal datasets help? Inter-annual Fluctuations Establishment and Colonization Dispersal, Invasion, Extinction, Reinvasion Time How can extensive spatial datasets help? Abundance or Infection Habitat Fragmentation Distance from Source Climate variable Change in Suitable Habitat Low Low Environmental Index High Some Sources of Data • • • • • • Meteorological Stations (climate, weather) Satellite – climate, vegetation, soil moisture, etc Census: population, age, sex, location, etc… Passive or active surveillance of human cases Surveillance of vector, reservoir abundance more... Knowing is not enough; we must apply. Willing is not enough; we must do. (Goethe)