Spatial distributions and patterns of Hantavirus Pulmonary Syndrome in the Western United States Público

Ervin, Beth (2013)

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Hantavirus Pulmonary Syndrome (HPS) is a rare disease in the United States with a high mortality rate of around ~40%. Spread most commonly through deer mice, exposure to virus particles occurs with inhalation of aerosolized rodent feces or contact with infected mice. HPS has been nationally notifiable since 1995 and some 600 cases have since been confirmed. Though deer mice are prevalent across the North American continent, human cases of HPS are not consistently spread; most cases occur in the western United States.

Previous studies have analyzed environmental characteristics and host behaviors, but neither monitoring of rodent density nor identification of common local environmental features appear to be enough in assessing HPS risk for humans. This study analyzes the distribution of human cases across four western States (Washington, Oregon, California, and Nevada) assessing the resulting patterns through spatial data analysis. Hot-spots of increased HPS occurrence were identified and a focused environmental model was built from remote sensing data to examine the local variables that may be influencing HPS cases around the Sierra Nevada Mountains.

Conclusions from this study highlight the importance of spatial relationships between human cases and cases to the environment. The importance in analyzing Hantavirus ecological studies with the inclusion of spatial descriptive statistics in human disease is in developing of more sensitive and accurate models to predict areas of high infection risk for humans.

Table of Contents

Table of Contents
Introduction 1
Literature review 2
Refugia 2
Temporal Influences 4
Landscape and Spatial Ecology 6
Purpose of Study 7
Methods 8
Study Design 8
Data Collection Methods 9
Analysis 13
Descriptive Analysis 13
Spatial Data Statistics 13
Assessment of Environmental Differences 18
Sierra Nevada Environmental Model 19
Results 20
Descriptive Analysis 20
Spatial Data Statistics 23
Environmental Differences 25
Sierra Nevada Modeling Results 27
Discussion 28
Limitations 32
Recommendations 36
Conclusions 38
Tables and Figures 39
Figure 1: Deer mouse habitat in North America 39
Figure 2: Diagnosed HPS cases in the US mapped by states of exposure 39

Figure 3: Percentage of HPS occurrence by State over Study Area 40
Table 1: Frequency and Percentage Statistics at the COUNTY level 40
Table 2: Frequency and Percentage Statistics at ZCTA level 40
Figure 4: HPS cases within Counties 41
Figure 5: HPS Crude Incidence by County 42
Figure 6: HPS Case Count by ZCTA 43
Figure 7: HPS Crude Incidence by ZCTA 48
Figure 8: Voronoi Map of ZCTA Centroids and Case Counts 53
Figure 9: Voronoi Map of ZCTA Centroids and Incidence Rate 54
Figure 10a: HPS Cases in ZCTA across USGS Ecological Zones 55
Figure 11a: HPS Cases in ZCTAs within Watershed Areas 57
Figure 12a: HPS Cases in ZCTAs across Elevation 59
Table 3: Global Moran's I for Case Counts 61
Table 4: Global Moran's I for Incidence Rate 62
Figure 13: Global Autocorrelation Spatial Correlogram for case counts 63
Figure 14: Global Autocorrelation Spatial Correlogram for Incidence Rate 63
Figure 15: Local Clustering of Case Counts 64
Figure 16: Significant Clustering of Case Counts 65
Figure 17: Local Clustering of Incidence Rate 66
Figure 18: Significant local clustering of Case Incidence Rate 67
Figure 19: Hot Spot Analysis of Case Counts 68
Figure 20: Hot Spot Analysis of Case Incidence Rates 69
Figure 21: Significant z-scores in Hot Spot Analysis of Case Counts 70
Figure 22: Significant z-scores in Hot Spot Analysis of Incidence Rates 71
Figure 23: Elevation 72
Figure 24: Ecological Zones 73
Figure 25: Annual Precipitation 74
Figure 26: Maximum Temperature Averages 1981-2010 75
Figure 27: Minimum Temperature Averages 1981-2010 76
Figure 28: Elevation/Flow Length/Cases in Hot Spots and ZCTA 77
Figures 29 a-d: Hydrology Model Building 78
Figure 30: Sierra Nevada Study Area 80
Table 5: Sierra Nevada Regression Analysis 80
References 81

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