Predicted probability of districts with West Nile Virus infections by the end of the 2015 transmission season, based on July 2015 temperature abnormalities.
This map can help delineate districts at risk for WNV transmission in 2015 based on a multivariate model with July 2015 temperature abnormality. The map illustrates the predicted probability of WNV infection per district. The association between WNV outbreaks in Europe and a number of temperature parameters such as mean, minimum and maximum and their anomalies were examined by Paz et al (2013) . Positive temperature anomalies[i] were found to be a major risk factor for WNV occurrence. Subsequently, in a study by Tran et al. (2014) remotely sensed mean temperature anomalies of July as well as remotely sensed water index anomalies of June were identified as a risk factors for WNV transmission in Europe .
Predictors in the multivariate model of the probability map included: July 2015 temperature deviation (data computed from NOAA NCEP-NCAR, US National Centre for Atmospheric Research), population, presence of wetlands, presence of birds’ migratory routes, June 2015 modified normalized difference water index[ii] and the occurrence of a WNV outbreak the previous year, as previously described . The nomenclature of territorial units for statistics classification (NUTS) was used to define a district as an administrative unit at level 3 with population estimate of 2010.
This map was generated in collaboration with Dr. Annelise Tran (CIRAD) and Dr. Shlomit Paz (University of Haifa).
1. Paz S, Malkinson D, Green MS, Tsioni G, Papa A, Danis K, Sirbu A, Ceianu C, Katalin K, Ferenczi E, Zeller H, Semenza JC (2013) Permissive summer temperatures of the 2010 European West Nile fever upsurge. PLoS One 8: e56398.
2. Tran A, Sudre B, Paz S, Rossi M, Desbrosse A, Chevalier V, Semenza JC (2014) Environmental predictors of West Nile fever risk in Europe. Int J Health Geogr 13: 26.
[i] Positive deviation computed by subtracting weekly mean temperature for July 2015 from the weekly perennial average temperature.
[ii] To derive the Modified normalized difference water index (MNDWI) values, Moderate Resolution Imaging Spectroradiometer (MODIS) data products were acquired from Land Process Distributed Active Archive Center (LP DAAC). MODIS Terra 8-day composite images of surface reflectance estimates at 500 m spatial resolution (product MOD09A1) were acquired.