I don't think disease was much of a factor. Darren Warner, in his 2013 Illinois deer forecast said, "Illinois hunters bagged 180,811 whitetails last fall, continuing an ongoing downward harvest trend in the Land of Lincoln since 2007. Last summer, epizootic hemorrhagic disease (EHD) killed whitetails throughout Illinois. Officials estimate over 3,000 deer in 87 counties succumbed to the disease.
Nonetheless, about 700,000 whitetails still call Illinois home, so hunters should have plenty of opportunity to fill their freezers in 2013.
“There are some West-Central and Southern counties that still have too many deer,” said Tom Micetich, deer project manager for the Illinois Department of Natural Resources. "
So going into 2013 season there sure were plenty of deer.