Karen Chávez and Sarah Bowman

USA TODAY Network

Last week, an expert in infectious disease suggested an ailment found largely in deer could impact humans.

During a hearing before lawmakers in Minnesota, Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, offered the warning on chronic wasting disease, which has been confirmed in 25 states.

"It is probable that human cases of chronic wasting disease associated with consumption with contaminated meat will be documented in the years ahead," said Osterholm. "It’s possible the number of human cases will be substantial, and will not be isolated events."

Here's everything you need to know about the "zombie" deer disease.

What is it?

CWD was first observed in the 1960s at a research facility in Colorado. It has now been confirmed in 24 states and two Canadian provinces as of January, said the Centers for Disease Control and Prevention.

CWD is a transmissible spongiform encephalopathy disease in deer, elk, moose and reindeer/caribou and always kills its victims. The source of the disease is an abnormal prion — a form of protein — that collects in the animal’s brain cells, according to the North Carolina Wildlife Commission. These brain cells eventually burst, leaving behind microscopic empty spaces in the brain matter that give it a “spongy” look.

The disease has no cure or preventative measures at this time, said Emily Wood, executive director of the Indiana Wildlife Federation. So if an animal is infected, it will die.

More:Why this deer disease could change the way Americans hunt forever

The disease is believed to spread through saliva, urine or feces from live deer or through contact with high-risk parts such as the backbone, eyes or spleen of harvested deer. The disease can spread through the natural movement of deer, Wood said, but it spreads farther and quicker when humans move the deer.

That most frequently is the case with captive deer hunting operations, where businesses will move deer from one state to another. A law was passed to allow fenced hunting in Indiana in 2015.

Despite the possible symptoms of the disease, it often can take years for the symptoms to show and be nearly impossible for a hunter to tell whether the deer is infected.

What's being done to combat CWD?

Several states have taken measures to prevent the spread of the disease.

In North Carolina, anyone transporting cervid (animals from the deer family) carcass parts into the state must follow processing and packaging regulations, which only allow the importation of:

Meat that has been boned out such that no pieces or fragments of bone remain

Caped hides with no part of the skull or spinal column attached

Antlers, antlers attached to cleaned skull plates, or cleaned skulls free from meat, or brain tissue

Cleaned lower jawbone(s) with teeth or cleaned teeth

Finished taxidermy products and tanned hides.

Also, everything must include labels with information such as the name and address of the hunter and the date the deer was killed. These new restrictions aim to prevent the infectious agent of CWD from contaminating new environments by way of disposal of carcass tissues, particularly those of the brain and spine, since CWD contaminants can last in the soil for years.

Meanwhile, Indiana has already stepped up its monitoring efforts, though testing is not mandatory. The Indiana Department of Natural Resources has identified several counties neighboring near where the deer has been detected in Michigan and Illinois for enhanced surveillance. In those areas, it is asking hunters to have their harvested deer tested for the disease.

Should people be worried?

According to the CDC, there have been no reported cases of CWD in people. Animal studies suggest some non-human primates like monkeys eating meat from infected animals or that come in contact with the blood or brains of an infected animal could face a risk. "These studies raise concerns that there may also be a risk to people," said the CDC.

More:Smith: With yet another CWD-positive deer farm, is it time to consider buyouts?

Karen Chávez reports for the Asheville (N.C.) Citizen-Times. Sarah Bowman reports for the Indianapolis Star. Contributing: Brett Molina, USA TODAY