Remotely-sensed Enviroclimatic patterns and Ebola outbreaks: linkages and early warning
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Transcript of Remotely-sensed Enviroclimatic patterns and Ebola outbreaks: linkages and early warning
Remotely-sensed Enviroclimatic patterns and Ebola outbreaks:
linkages and early warning
Dan Slayback
Jorge Pinzon
Compton Tucker
8 September 2004
Biospheric Science Branch, Code 923NASA Goddard Space Flight CenterGreenbelt MD 20771 USA
Outline
• Ebola outbreaks: facts and hypotheses• Environmental links to remotely sensed data• Spatial & temporal specificity of
environmental trigger events• Conclusions
From: Trigger events: enviroclimatic coupling of Ebola hemorrhagic fever outbreaks. 2004. JE Pinzon, JM Wilson, CJ Tucker, R Arthur, PB Jahrling, and P Formenty, American Journal of Tropical Medicine and Hygiene. (in press)
•Many Ebola outbreaks have occurred Many Ebola outbreaks have occurred in African closed tropical forestin African closed tropical forest
•Some Ebola outbreaks have occurred Some Ebola outbreaks have occurred in African gallery tropical forest in African gallery tropical forest within a savanna matrixwithin a savanna matrix
Outbreak Severity
385 21079 47
Outbreak Locations
Community Epidemic Scenario Secondary transmission within species.Secondary transmission within species.Reciprocal transmission between species.Reciprocal transmission between species.
APES/HUMANS
INTERMEDIATEHOST
RESERVOIR
“Cul de Sac” Hosts
Cul de Sac HOST--Cul de Sac HOST--HUMANSHUMANS?
RESERVOIR
APESAPES
Just because a species tests positive for virus or Just because a species tests positive for virus or antibodies does not mean that it is a link in the antibodies does not mean that it is a link in the chain of transmission to apes.chain of transmission to apes.
Peter Walsh et al. Peter Walsh et al. NatureNature (2003) (2003)
Transmission Scenarios
Possible Ebola Transmission(s)no usual suspects!
It is unknown where the virus dwells…
NOAA 11AVHRR
1980 200019901985 201020051995
NOAA 7AVHRR
NOAA 9AVHRR
NOAA 14AVHRR
SeaWiFS
SPOT
MODISes
NOAA-16AVHRR NPOESSNPOESS
NOAA9NOAA9
Moderate-resolution (1-10’s kms) environmental satellites
Environmental Links withRemotely Sensed Data:
available datasets
NOAA AVHRR 8-km NDVI Data Set
Radiation
VIS/NIR/SWIR Band Comparison
AVHRR
SeaWiFS
SPOT-VGT
MODIS
New, improved 8-km AVHRR NDVI data set 1981-present
2003
pal: est ndvi = 0.002*year - 0.020
gimms: est ndvi = 0.0007*year - 0.007-0.04
-0.03
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
1982 1984 1986 1988 1990 1992 1994 1996 1998 2000
GIMMS-E
PAL
Ye
Major Dataset Differences
Global NDVI anomalies
Are there unique environmental characteristics at outbreak sites, during the outbreak year?
Hypothesis: very extreme change from rainy to dry season
1994 Ebola Outbreak Locations NDVI Time Series
Mean time series and anomalies
Spatial signatures and risk
CCA is a method that maximizes the variance between two datasets. Here, we use CCA to identify areas and times that exhibit enviroclimatic signals typical of those at known outbreak sites and dates.
CCA(A) = [U,S,V]
A: paired-mode correlation matrix between yearly NDVI signals and corresponding NDVI signals from the outbreak sites at outbreak years.
U: orthonormal vector of satellite NDVI signals
S: percentage of covariance explained by canonical factors
V: orthonormal vector of Ebola sites
The analysis conducted only over areas with high enviroclimatic correlation to previous outbreak sites (r2 > 0.95)
Canonical Correlation Analysis (CCA)
Trigger Trigger event event
summarysummary∑
=
Nc
j
NcjVNcNcSNcU1
)':1,():1,:1():1(:,
the the hot hot
zonezone