disease patterns and distribution. outline 1.introduction: infectious disease epidemiology...
TRANSCRIPT
Disease Patterns and Distribution
Outline
1. Introduction: Infectious Disease Epidemiology
2. Patterns of Environmental Influences
3. Climate as an Environmental Driver
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
Agent
Host
Environment
Classical Epidemiological Triad
Agent(diverse exposures,
including non-contagious )
Host(animal, plant,
ultimately human)
Environment*(biophysical, psycho-social, etc.)
*CLIMATE is an Environmental Influence
Environment
Agent
Host
Environment
host distribution, abundance, infection
longevity & infectivityoutside host
e.g. cholera hantaviral disease
hookwormschistosomiasis
Agent
nutrition
treatment
e.g. TB, HIV/AIDS,diarrheal diseases,acute respiratory
infections
housing
hygiene
Host
tissue tropisms,pathogenicity, immune response,host specificity
e.g. rabies, Lyme disease,
malaria, cryptosporidiosi.
Examples Involving Infectious Diseases
Agent
Host
Environment
Altered hygiene
Redesigned housing
Better nutrition
Improved irrigation
But for ALL diseases, complex interactions occur...
Agent
Host
Environment
Agent transport to new areas
New antibiotics, pesticides
Labor actions affecting toxin exposure
Agent
Host
Environment
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
Social and Economic Policies
Physical Enviro
nment
Institutions (including medical care)
Living Conditions
Social Relationships
Individual Risk Factors
Genetic/ConstitutionalFactors
Pathophysiologicpathways
Individual/PopulationHealth
Environmental Determinants of Human Disease
Modified from Kaplan, 2002
Social and Economic Policies
Climate?
Institutions (including medical care)
Living Conditions
Social Relationships
Individual Risk Factors
Genetic/ConstitutionalFactors
Pathophysiologicpathways
Individual/PopulationHealth
Research Challenge – Analyze and understand interactions!
What is climate change? Climate variability?
Time
En
viro
nm
enta
l Var
iab
le
Low
High
Average Trend(solid line)
Actual Measure(dashed line)
Unchanging Average, Unchanging Extremes
Time
En
viro
nm
enta
l Var
iab
le
Low
High
Average Trend(solid line)
Actual Measure(dashed line)
Unchanging Average, Increasing Extremes
Time
En
viro
nm
enta
l Var
iab
le
Low
High
Average Trend(solid line)
Actual Measure(dashed line)
Increasing Average, Unchanging Extremes
Time
En
viro
nm
enta
l Var
iab
le
Low
High
Average Trend(solid line)
Actual Measure(dashed line)
Different Rates of Increasing Averages
Time
En
viro
nm
enta
l Var
iab
le
Low
High
Average Trend(solid line)
Actual Measure(dashed line)
Increasing Average, Greater Extremes
Time
En
viro
nm
enta
l Var
iab
le
Low
High
Average Trend(solid line)
Actual Measure(dashed line)
Increasing Rate of Increasing Average, Unchanging Extremes
Time
En
viro
nm
enta
l Var
iab
le
Low
High
Average Trend(solid line)
Actual Measure(dashed line)
Increasing Rate of Increasing Average, Greater Extremes
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 ).
Anthroponotic Infections
Zoonotic Infections
Direct Exposure Indirect ExposureEnvironmental Exposures
Vehicle
Humans
Source
Stream pollutantsAir ParticulatesLegionella
Humans
Humans STDsMeaslesHepatitis B
Vehicle
Humans
Humans
Vehicle
MalariaDengueRoundworm
Vehicle Vehicle
Animals
AnimalsHumans Lyme Disease
Hantaviral DiseaseMost arboviral diseases
Animals
Animals
HumansAnthraxEbola (?)CJD
Environment and Exposure
Source
Humans Solar UVEM RadiationTetanus
Direct Exposure Indirect Exposure
Environmental Exposures
Source
Humans Solar UVEM RadiationTetanus
Vehicle
Humans
Source
Stream pollutantsAir ParticulatesLegionella
Environment and ExposureWhere might Climate Impact?
Anthroponotic Infections
Direct Exposure Indirect Exposure
Humans
Humans STDsMeaslesHepatitis B
Vehicle
Humans
Humans
Vehicle
MalariaDengueRoundworm
Environment and ExposureWhere might Climate Impact?
Zoonotic Infections
Direct Exposure Indirect Exposure
Vehicle Vehicle
Animals
AnimalsHumans Lyme Disease
Hantaviral DiseaseMost arboviral diseases
Animals
Animals
HumansAnthraxEbola (?)CJD
Environment and ExposureWhere might Climate Impact?
Elements of Climate and Health
Maximum Temperature
Minimum Temperature
Mean Temperature
Rainfall Amount
Rainfall Frequency
Rainfall Rate
Heat-related mortality
Extreme Events
Air Pollution
Vector-borne Diseases
Water-borne Diseases
Agricultural Production
What diseases are climate sensitive?
• More sensitive– Which are more
sensitive????High
Moderate
Sen
siti
vity
• Less sensitive– What about less
sensitive???Low
Lowest
Sen
siti
vity
What diseases are climate sensitive?
• More sensitive– heat stress
– effects of storms
– air pollution effects
– asthma
– vector-borne diseases
– water-borne diseases
– food-borne diseases
High
Moderate
Sen
siti
vity
• Less sensitive– sexually transmitted
diseases
– violence
– most cancers
– atherosclerosis
– tuberculosis
– myocardial infarction
Low
Lowest
Sen
siti
vity
More Climate Sensitive
Heat stress
Asthma
Vector-borne Disease
Water-borne disease
Myocardial Infarction
Cancer (not skin)
Sexually transmittedDisease
Atherosclerosis
Violence
Effects of Storms
Food-borne disease
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 non-existent, especially in developing countries)
• Inference of climate-disease links limited without carefully considering time-space patterns
aa bb
cc dd
Interpreting Spatial Patterns of Risk
•Area of risk
•Size of areas
•Location and pattern
•Inter-area distances
•Connectivity among locations
How can extensive time-space datasets help?
T1
T2
T3
Pattern of disease… or knowledge, SES,exposure, etc...
How can extensive time-space datasets help?
How can extensive temporal datasets help?
Time
Ab
un
dan
ce /
Pre
vale
nce
How can extensive temporal datasets help?
Establishmentand Colonization
Dispersal, Invasion, Extinction, Reinvasion
Inter-annualFluctuations
Time
Ab
un
dan
ce /
Pre
vale
nce
Environmental Index
Ab
un
dan
ce o
r In
fect
ion
Low High
Low
High
Habitat Fragmentation
Change inSuitable Habitat
Distancefrom Source
Climate variable
How can extensive spatial datasets help?
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)