In a state where hunting is so popular that some high schools dismiss classes to let students take to the woods, it's unusual that an outdoors group would have to put up billboards encouraging people to go hunting.

Doing so is one indication of the concern of over chronic wasting disease, an incurable brain disease that is fatal to deer and was discovered in Wisconsin's whitetail herd eight months ago.

Experts say there is no scientific evidence the disease can infect humans, but the World Health Organization advises people not to eat any part of a deer with evidence of the disease.

Wildlife managers and others are worried that thousands of deer hunters might stay home this fall -- which could jeopardize a $1 billion industry and perhaps lead to fewer deer killed from an overpopulated herd.

The outdoors group Whitetails Unlimited bought space on 100 billboards for this message: "Fight CWD by continuing to hunt deer" and is spending $300,000 on a campaign that will also include bumper stickers, executive director Pete Gerl said.

So far this year, the number of deer-hunting licenses sold was down 23 percent, or 120,000 licenses, as the first major hunting season -- a four-day, doe-only hunt in about one-third of the state where deer populations are too high -- ended Oct. 27.

"Clearly we are concerned. There is no question about that," state Department of Natural Resources Secretary Darrell Bazzell said.

Gander Mountain, which operates 13 sporting goods stores in Wisconsin, added messages to its newspaper and radio advertisements encouraging people to hunt and set up kiosks in its stores with information about chronic wasting disease, spokesman Mike Sidders said.

"The fact that hunters are considering not hunting is a crisis. No question about it," Sidders said from the company's headquarters in Bloomington, Minn.

Bill Rose, of Sussex, has hunted for 48 years. He said he intends to go hunting this year, too -- "but I still don't know whether I am going to shoot a deer because of concerns about the meat."

The disease creates some spongelike holes in the deer's brain, causing the animal to grow thin, act abnormal and die.

In February, the DNR announced that three bucks shot just west of Madison had the disease, the first time it was discovered east of the Mississippi River. So far, the state has found 40 infected deer in a 411-square-mile area and wants hunters to kill all the deer -- at least 25,000 -- to try and eradicate the disease. That hunting began last Thursday in a season that runs through Jan. 31.

Hunting in the rest of the state will take place in the tradition-bound nine-day season that opens Nov. 23. It is like a big family reunion, attracting 650,000 to 700,000 hunters to the fields and woods. What hunters spend ripples through the economy to the tune of $1 billion, a federal study estimated.

The illness doesn't appear to be scaring off hunters in other states.

In Colorado, where chronic wasting disease was found in the 1960s but resurfaced only recently, state wildlife officials said the number of applications for deer and elk licenses is up.

Wyoming, South Dakota, Montana and New Mexico -- other states dealing with chronic wasting disease -- say they have observed no impact on hunter interest or license sales.

Wisconsin outdoors officials are hopeful that as hunters get more of their worries and fears addressed about the so-called mad deer disease, they will be less leery about hunting.

At O-W Sports and Liquor in Owen, clerk Heida Bjork said it's too early to push any panic buttons.

"That last week before the gun deer season, we will sell hundreds of licenses," she said. "A lot of people wait until that last week and they always will."

Hunters bring in a deer shot in a chronic wasting disease zone to a Wisconsin field station last month.