“When there is an increase in the mosquito infection rate, an
increase in the number of human cases of the virus can be
expected,” said Nancy Westcott, research climatologist at the
Midwestern Regional Climate Center, University of Illinois, and
one of the leaders in making the models available.
The Illinois mosquito infection rate models can be found online
The statewide models were designed using a successful approach
that Marilyn O'Hara Ruiz, director of the Geographic Information
Systems and Spatial Epidemiology Laboratory at the College of
Veterinary Medicine, had developed for DuPage County, with
Lindsay Shand, a graduate student in statistics.
Basically, last month’s weather is used to predict this week’s
mosquito infection rate. The models rely on the relationship
between weather parameters and measured historic mosquito
infection rates; the measured mosquito infection rate data are
from mosquito testing programs conducted by local public health
districts and reported by the Illinois Department of Public
Using current weather data, National Weather Service temperature
(10-day) and precipitation (3-day) forecasts, and last year’s
seasonal temperature and precipitation values, the models are
able to predict mosquito infection rates one to two weeks
earlier than is possible by directly measuring mosquito
infection through testing programs.
Westcott, Ruiz, and epidemiology doctoral student Surendra Karki
created the models found on the new website, which show
predictions of mosquito infection rate over time, measured
mosquito infection rate when available, and, for comparison, the
rate for a “high” WNV year (2012) and ten-year average mosquito
infection rate in the nine Illinois climate areas.
The goal in releasing this public website is to make data
available to public health districts that issue warnings about
the virus, as well as to anyone who is concerned about West Nile
“This website is one way to put science into action,” noted
Ruiz. “We created a strong predictive model for DuPage County,
and by releasing the statewide models we hope to make that
research accessible and relevant to the public.”
The researchers are hoping for feedback from public health
departments and users across the state so that the models for
each region can be refined.
“The nine regional models can still be improved, but we want to
share what we have learned so far and improve these as we learn
more,” said Ruiz.
The website also offers links to the DuPage County model and one
developed for Champaign County using a different data approach.
In addition, the site links to statewide resources related to
West Nile virus. Funding to develop the website and models was
provided by the Prairie Research Institute, the Wheaton Mosquito
Abatement District, the DuPage County Health Department, the
Forest Preserve District of DuPage County, and the National
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The new models indicate that fewer Illinoisans will experience
infections this year compared with the high infection rate seen in
2012, although there could still be a moderate number of human cases
of the virus in Illinois, depending on the weather in August.
As of August 2, three human cases of the virus have been reported in
Illinois, and 23 counties have mosquitoes that have tested positive
as carriers for the virus, according to the IDPH.
From 5 to 185 severe cases of WNV have occurred in Illinois each
year since 2004. Hot, dry summers are the best climate conditions
for Culex pipiens, the type of mosquito that transmits WNV to
Mild cases of the West Nile virus may cause a slight fever or
headache. More severe infections may cause a high fever with head
and body aches, disorientation, tremors, convulsions, and, in the
most severe cases, paralysis or death. Usually symptoms occur from
three to 14 days after the bite of an infected mosquito.
Transmission of the virus to humans typically starts in late July.
The Culex mosquito is most active from dusk to dawn, so the risk is
highest during those hours.
The Culex mosquitoes are a container species—breeding in small,
man-made bodies of water, such as old tires, bird baths, clogged
gutters, and container plants holding excess water. Such areas
should be drained to help decrease the population of virus carriers.
[© 2016 Thomson Reuters. All rights
Prairie Research Institute: The Prairie Research Institute (PRI)
at the University of Illinois at Urbana-Champaign comprises the
Illinois Natural History Survey, Illinois State Archaeological
Survey, Illinois State Geological Survey, Illinois State Water
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objective natural and cultural resource expertise, data, research,
service, and solutions for decision making, the stewardship of
Illinois’ resources, and the public good. www.prairie.illinois.edu
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