The paradoxical impact of drought on West Nile virus risk: Insights from long-term ecological data
Data files
Aug 08, 2025 version files 22.06 MB
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abund_quin_panel_clean.csv
1.62 MB
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abund_quinq_full_clean.csv
4.12 MB
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abund_tar_full_clean.csv
4.72 MB
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abund_tar_panel_clean.csv
1.64 MB
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arbonet_ca_clean.csv
38.27 KB
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climate_full_clean.csv.zip
8.10 MB
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landuse_clean.csv
16.90 KB
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pesticide_kernco_clean.csv
143.46 KB
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README.md
15.61 KB
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trapstation_info_clean.csv
7.76 KB
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wnvdroughtkern_analysis_v2.Rmd
23.23 KB
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wnvdroughtkern_figures_v2.Rmd
63.62 KB
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wnvmir_quin_panel_clean.csv
1.04 MB
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wnvmir_tar_panel_clean.csv
501.70 KB
Abstract
Mosquito-borne diseases are deeply embedded within ecological communities, with environmental changes – particularly climate change – shaping their dynamics. Increasingly intense droughts across the globe have profound implications for the transmission of these diseases, as drought conditions can alter mosquito breeding habitats, host-seeking behaviors, and mosquito-host contact rates. To quantify the effect of drought on disease transmission, we use West Nile virus (WNV) as a model system and leverage a robust mosquito and virus dataset consisting of over 500,000 trap nights collected from 2010-2023, spanning a historic drought period followed by atmospheric rivers. We pair this surveillance dataset with a novel modeling approach that incorporates monthly changes in bird host community competence, along with drought conditions, to estimate the effect of drought severity on WNV risk using panel regression models. Our results show that while drought decreases mosquito abundances, it paradoxically increases WNV infection rates. This counterintuitive pattern likely stems from reduced water availability, which concentrates mosquitoes and pathogen-amplifying bird hosts around limited water sources, thereby increasing disease transmission risk. However, the magnitude of the effect depends critically on mosquito species, suggesting species-specific behavioral traits are key to understanding the effect of drought on mosquito-borne disease risk across real landscapes.
Dataset DOI: 10.5061/dryad.b8gtht7qn
Description of the data and file structure
Title: The paradoxical impact of drought on West Nile virus risk: insights from long-term ecological data
Authors: S Sambado*, T J Sipin, Z Rennie, A Larsen, J Cunningham, A Quandt, D Sousa, and A J MacDonald
*corresponding author: sbsambado@ucsb.edu / ssambado@stanford.edu
Description: Observational study using vector control surveillance data paired with environmental data to assess the effect of drought on mosquito abundances and infection rates in Kern County from 2010-2023. Within-estimator panel models (also known as "fixed-effects" in econometrics) found that an increase in drought severity led to a decrease in mosquito abundances and an increase in West Nile virus infection rates.
Included files: To re-create figures and analyses from the resulting manuscript, users can download the data files (*.csv) and run the scripts (wnvdroughtkernfigures_v2.Rmd and wnvdrought_analysis**v2.Rmd).
Software: R version 4.4.1
*package versions: *broom_1.0.5, fixest_0.12.1, ggplot2_3.5.2, ggmap_4.0.0, ggpubr_0.6.0, modelsummary_2.1.0, RColorBrewer_1.1-3, readr_2.1.5, sandwich_3.1-0, tidyverse_2.0.0
Files and variables
File: wnvdroughtkern_figures_v2.Rmd
Description: script to re-create figures
File: wnvdroughtkern_analysis_v2.Rmd
Description: script to re-create data summaries and analyses
File: abund_quin_panel_clean.csv
Description: Cx. quinquefasciatus abundance data for panel models
Variables
- :
- clust: assigned clusterID to individual trap station
- year: year of collection
- month: month of collection
- lat: latitude of clusterID
- lon: longitude of clusterID
- species: species of mosquito (Cx. tarsalis or Cx. quinquefasciatus)
- mos_per_trap_night: average mosquito count per trap night within a month
- pdsi: Palmer Drought Severity Index (e.g., drought severity metric)
- temp_max_c: maximum temperature (C)
- woy_cms_mean: average weekly Kern River discharge rate (cms) within a month
- pdsi_standardized: standardized Palmer Drought Severity Index
- temp_max_c_standardized: standardized maximum temperature (C)
- woy_cms_mean_standardized: standardized average weekly Kern River discharge rate (cms) within a month
- pdsi_standardized_lag_1month: standardized Palmer Drought Severity Index from the prior month
File: abund_quinq_full_clean.csv
Description: Cx. quinquefasciatus abundance data for figure making
Variables
- :
- clust: assigned clusterID to individual trap station
- year: year of collection
- collection_date: date of collection
- month: month of collection
- species: species of mosquito (Cx. tarsalis or Cx. quinquefasciatus)
- trap_nights: number of trap nights an individual trap station was deployed for surveillance efforts
- total_mosquitoes: number of mosquitoes collected per trapping effort
- mos_per_trap_night: weekly average mosquitoes collected per trap night within a month
File: arbonet_ca_clean.csv
Description: data on reported human WNV disease cases in California from CDC ArboNET
Variables
- :
- full_geo_name: county identifier
- year: year of reported cases
- county: county of reported cases
- activity: type of report (human activity or non-human activity)
- reported_human_cases: number of reported human West Nile virus cases
File: landuse_clean.csv
Description: data on land use types for trap station clusters
Variables
- :
- lon: longitude of trap station
- lat: latitude of trap station
- land_use2020: full descriptor of land use under the trap station
- land_bin2020: binned category of land use under the trap station
File: abund_tar_full_clean.csv
Description: Cx. tarsalis abundance data for figure making
Variables
- :
- clust: assigned clusterID to individual trap station
- year: year of collection
- collection_date: date of collection
- month: month of collection
- species: species of mosquito (Cx. tarsalis or Cx. quinquefasciatus)
- trap_nights: number of trap nights an individual trap station was deployed for surveillance efforts
- total_mosquitoes: number of mosquitoes collected per trapping effort
- mos_per_trap_night: weekly average mosquitoes collected per trap night within a month
- pdsi: Palmer Drought Severity Index (e.g., drought severity metric)
File: trapstation_info_clean.csv
Description: data on trap station location information
Variables
- :
- id: individual trap station ID
- clust: assigned clusterID for trap station
- lat: latitude of clusterID centroid
- lon: longitude of clusterID centroid
File: pesticide_kernco_clean.csv
Description: data on pesticide activity in Kern County
Variables
- :
- year: year of pesticide application
- month_in_year: month of pesticide application
- pounds_chemical_applied: pounds of pesticide applied
- mos_life_stage_target: pesticide targeted mosquito life stage (larvicide or adulticide)
File: abund_tar_panel_clean.csv
Description: Cx. tarsalis abundance data for panel models
Variables
- :
- clust: assigned clusterID to individual trap station
- year: year of collection
- month: month of collection
- lat: latitude of clusterID
- lon: longitude of clusterID
- species: species of mosquito (Cx. tarsalis or Cx. quinquefasciatus)
- mos_per_trap_night: average mosquito count per trap night within a month
- pdsi: Palmer Drought Severity Index (e.g., drought severity metric)
- temp_max_c: maximum temperature (C)
- woy_cms_mean: average weekly Kern River discharge rate (cms) within a month
- pdsi_standardized: standardized Palmer Drought Severity Index
- temp_max_c_standardized: standardized maximum temperature (C)
- woy_cms_mean_standardized: standardized average weekly Kern River discharge rate (cms) within a month
- pdsi_standardized_lag_1month: standardized Palmer Drought Severity Index from the prior month
File: wnvmir_tar_panel_clean.csv
Description: Cx. tarsalis WNV infection data for panel models
Variables
- :
- clust: assigned clusterID to individual trap station
- year: year of collection
- month: month of collection
- lat: latitude of clusterID
- lon: longitude of clusterID
- species: species of mosquito (Cx. tarsalis or Cx. quinquefasciatus)
- mir: minimum West Nile virus infection rate of the tested mosquito pool
- pdsi_standardized: standardized Palmer Drought Severity Index
- temp_max_c_standardized: standardized maximum temperature (C)
- woy_cms_mean_standardized: standardized average weekly Kern River discharge rate (cms) within a month
- mean_competence_standardized: standardized average weekly bird community competency index within a month
- mean_competency: average weekly bird community competency index within a month
- pdsi_standardized_lag_1month: standardized Palmer Drought Severity Index from the prior month
File: wnvmir_quin_panel_clean.csv
Description: Cx. quinquefasciatus WNV infection data for panel models
Variables
- :
clust: assigned clusterID to individual trap station - year: year of collection
- month: month of collection
- lat: latitude of clusterID
- lon: longitude of clusterID
- species: species of mosquito (Cx. tarsalis or Cx. quinquefasciatus)
- mir: minimum West Nile virus infection rate of the tested mosquito pool
- pdsi_standardized: standardized Palmer Drought Severity Index
- temp_max_c_standardized: standardized maximum temperature (C)
- woy_cms_mean_standardized: standardized average weekly Kern River discharge rate (cms) within a month
- mean_competence_standardized: standardized average weekly bird community competency index within a month
- mean_competency: average weekly bird community competency index within a month
- pdsi_standardized_lag_1month: standardized Palmer Drought Severity Index from the prior month
File: climate_full_clean.csv.zip
Description: data on climate summaries in Kern County used for figure making. The user will have to unzip the file before using.
Variables
- :
- clust: assigned clusterID to individual trap station
- year: year of collection
- water_year: year of rain season (starts in November, ends in March)
- tmmx_C: maximum temperature (C)
- pr*_sum_wateryear*: sum of precipitation (mm) during water year (November through March)
Code/software
R version 4.4.1
package versions
- broom_1.0.5
- fixest_0.12.1
- ggplot2_3.5.2
- ggmap_4.0.0
- ggpubr_0.6.0
- modelsummary_2.1.0
- RColorBrewer_1.1-3
- readr_2.1.5
- sandwich_3.1-0
- tidyverse_2.0.0
Access information
Other publicly accessible locations of the data:
Data was derived from the following sources:
References: (1) Fink et al. 2022, (2) Abatzoglou 2013, (3) Friedl 2022