RESEARCH: WEST NILE VIRUS IN ILLINOIS

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CHAMPAIGN-URBANA CROSSOVER MODEL
Experimental Data, for Champaign-Urbana Only — 2017

Models from
Previous Years:

About the Crossover Dates
Project and Models

culex pipiens
Culex pipiens - Northern House Mosquito.
Photo courtesy Robin McLeod.

The white-spotted mosquito Culex restuan and the northern house mosquito Culex pipien are believed to maintain the natural transmission cycle of West Nile Virus between birds and mosquitoes in Illinois. During the spring and early
summer, the white-spotted mosquito is the dominant species and is responsible for mosquito-bird-mosquito transmission of WNV. As the weather warms, the northern house mosquito becomes more dominant. The female of this later species is probably responsible for the rapid amplification of the arbovirus among birds and may act as the major bridge vector to mammals, including humans in the Midwest. Two temperature-based climate models were developed to estimate the likely date when the northern house mosquito begins to become the dominant species, and thus when the risk of WNV to horses, humans, and other wildlife is likely to increase.

The information provided here is based on research conducted by scientists at the Midwestern Regional Climate Center at the Illinois State Water Survey and in the Entomology Laboratory of the Illinois Natural History Survey.  This research is described in the following publication:

Kunkel, K.E., R. Novak, R. Lampman, and W. Gu, 2006:  Modeling the impact of variable climatic factors on the crossover of Culex Restuans and Culex Pipiens (Diptera Culicidae) vectors of West Nile Virus in Illinois.  American Journal of Tropical Medicine and Hygiene, 74, 168-173.

Westcott, N.E., and S.D. Hilberg, R.L. Lampman, B. W. Alto, A. Bedel, E.J. Muturi, H. Glahn, M. Baker,  K.E., Kunkel, R.J. Novak, 2011:  Predicting the Seasonal Shift in Mosquito Populations Preceding the Onset of the West Nile Virus in Central Illinois, Bulletin of the American Meteorological Society, 92,1173-1180.


MAXIMUM TEMPERATURE EXCEEDANCE MODEL (Threshold of 80°F):

How to interpret the model results -

81°F MAX TEMP MODEL - CURRENT (6/21/2017) MODEL RUN:
Based on this model, there is:  
    • a 50 percent chance that the crossover date will be later than July 31, 2017
    • a 90 percent chance it will be earlier than August 12, 2017
    • and a 10 percent chance it will be earlier than July 26, 2017
    • The current run of the model has a median crossover date of July 31, 2017
    • The earliest crossover date projected by the current model run is July 25, 2017
    • The latest crossover date projected by the current model run is August 27, 2017
   

Model Run History for the Current Year -

81°F Max Temp Model
Model Run Date 2017 Probability that crossover will occur earlier than given date
Earliest 10 percent 25 percent MEDIAN 75 percent 90 percent Latest
5/10 7/13 7/24 7/28 8/5 8/18 8/26 9/29
5/17 7/16 7/23 7/28 8/5 8/18 8/28 9/25
5/24 7/20 7/26 7/31 8/7 8/19 8/28 9/23
5/31 7/25 7/30 8/3 8/10 8/20 8/30 9/25
6/7 7/21 7/25 7/29 8/2 8/11 8/22 9/15
6/14 7/24 7/26 7/29 8/2 8/10 8/16 9/10
6/21 7/25 7/26 7/28 7/31 8/6 8/12 8/27

Graph of 81F Max Temp Model Data


DEGREE DAY MODEL:

How to Interpret the Model Results -

DEGREE DAY MODEL - CURRENT (6/21/2017) MODEL RUN:
Based on the current model run there is:
    • a 50 percent chance that the crossover date will be later than August 9, 2017
    • a 90 percent chance it will be earlier than August 22, 2017
    • and a 10 percent chance it will be earlier than July 28, 2017
    • The current run of the model has a median crossover date of August 9, 2017
    • The earliest crossover date projected by the current model run is July 18, 2017
    • The latest crossover date projected by the current model run is September 6, 2017

Model Run History for the Current Year -

Degree Day Model
Model Run Date 2017 Probability that crossover will occur earlier than given date
Earliest 10 percent 25 percent MEDIAN 75 percent 90 percent Latest
5/10 7/10 7/20 7/28 8/8 8/20 8/27 9/17
5/17 7/13 7/24 8/2 8/11 8/23 9/1 9/18
5/24 7/19 7/27 8/4 8/13 8/24 9/1 9/16
5/31 7/19 7/28 8/4 8/13 8/23 8/30 9/15
6/7 7/18 7/24 8/1 8/10 8/18 8/24 9/11
6/14 7/17 7/25 7/31 8/9 8/15 8/22 9/6
6/21 7/18 7/28 8/2 8/9 8/15 8/22 9/6


Graph of Degree Day Model Data


These graphs show the results of the individual model runs so far this season. As more of the “actual” weather is included in the model runs (i.e. as the summer progresses) and less “probable” weather (i.e. past climatology) is included, the plots of the dates will tend to converge on the crossover date.

NOTE: These models were derived from Champaign-Urbana, Illinois data. The threshold temperature may vary regionally.

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