Health officials in Hood River County, Ore., are investigating three cases of a rare and fatal brain disease known as Creutzfeldt-Jakob disease.

Two people have died and a third person is showing symptoms consistent with the disease. The disease has been confirmed in one of the deceased through an autopsy; the other two cases are considered probable, according to a statement from the Hood River County Health Department.

All three cases were diagnosed in the last eight months. County health officials declined to provide particulars about the individuals, such as their age, gender or town of residence.

“At this time, there is no identifiable link between these three cases,” a Hood River County statement said. The county has a population of about 24,000.

Creutzfeldt-Jakob disease is a neurodegenerative disorder caused by misfolded proteins known as prions. These prions lead to rapid brain deterioration, resulting in severe neurological symptoms and death. Although the disease is known for its sporadic occurrence, clusters raise concerns among public health officials about potential environmental or dietary exposure.

Symptoms include issues with memory, walking, coordination, speech and behavior changes, according to experts. It does not spread through the air, water, touch or social contact, according to Hood River County health officials.

The disease is considered incurable and is always fatal. Roughly 350 cases are diagnosed in the United States every year, according to the National Institutes of Health.

The disease is rare in people, affecting roughly 1.4 people per million. However, because the disease takes years to develop, any person’s chance of developing the disease is closer to 1 in 5,000 or 6,000, said Michael Geschwind, a professor of neurology at UC San Francisco in the Memory and Aging Center.

The disease is similar to chronic wasting disease, or CWD, which is also a prion-fueled disease, and was detected for the first time in wild deer in California and Washington last year.

CWD was first reported in 1967, in a captive Colorado deer. It has since spread to deer in 36 states. There are no known cases of the disease in Oregon wildlife.

For decades there has been concern that CWD could move into human populations through the ingestion of contaminated meat.

That’s because in the 1980s, a prion disease in sheep, known as scrapies — which humans do not seem to get — moved into cows, and soon people throughout the United Kingdom, France and elsewhere were becoming infected with mad cow disease, or bovine spongiform encephalopathy.

Since then, public health officials from the Centers for Disease Control and Prevention and several states have been paying close attention to clusters of Creutzfeldt-Jakob disease — investigating outbreaks to determine whether infected deer, elk or moose meat was involved.

They — and researchers from other agencies, such as the U.S. Geological Survey’s National Wildlife Health Center — also have been monitoring wild deer populations and keeping tabs on hunters who may have been exposed.

Although widespread geographically throughout the United States and Canada, the disease is considered relatively rare in wild populations of deer, elk and moose, said Brian Richardson, the emerging-disease coordinator at the USGS wildlife center.

“It may well be [in Oregon], but it’s hard to find rare events,” he said.

To date, there are no known incidents of people acquiring a prion disease by consuming deer, elk or moose meat, said Geschwind, the UCSF professor.

He said roughly 85% to 90% of Creutzfeldt-Jakob cases are considered sporadic, with no identified cause or source of infection. In 10% to 15% of the cases, the disease appears to be genetically inherited — with some people acquiring mutations associated with the disease.

However, there have been a few cases in which sources of infection or contamination have been identified, and almost all of them were from a medical mishap.

Prions are notoriously difficult to inactivate or destroy — withstanding standard sterilization techniques — and can remain intact for months and years on a surface, Geschwind said.

In a small number of cases, he said, people acquired the disease as a result of contaminated and improperly cleaned surgical equipment. In a few other cases, it was acquired by people who used products — such as growth hormone, or who received corneal transplants — derived, inadvertently, from infected cadavers.

It’s these proteins’ durability and longevity that have many researchers worried. Studies have shown that deer that harbor the disease can pass the infectious prions to other deer through saliva, blood, urine and feces.

“So, if the animal is licking a plant or licking a salt lick, for example, and another animal comes along and licks that plant or salt lick, then that might be a way of spreading the disease,” Geschwind said.

In addition, the decomposing body of a deer that died of the disease can infect the surrounding environment where the animal expired — potentially contaminating plants, seeds, fungi and soil, Richardson said.

He said not only is there the issue of surface contamination, but also research has shown that the proteins can “be taken up via rootlets and deposited in aerial plant tissues. Whether these plants contribute to chronic wasting disease transmission and what type of risk these plants pose to humans remain open questions.”

Geschwind noted that the work done by federal researchers to better understand the disease, provide diagnostic autopsies on presumptive cases, monitor wildlife and investigate clusters has provided a level of protection for the American public, which could be destabilized by proposed cuts to federal agencies.

“The idea of cutting government funding of rare disease is very short-sighted, because even though CJD is a rare disease, what we have learned from prion diseases has implications for all neurodegenerative diseases,” he said, noting Alzheimer’s disease, frontotemporal dementia, Parkinson’s disease and multiple system atrophy.

“All these diseases act in a prion-like manner in which normal proteins misfold, and those misfolded proteins cause the cells to not work partly and lead to disease,” he said. “But the basic mechanism that we’ve learned from this very rare disease applies to diseases that are thousands of times more common. To get rid of the research? It’d be a very grave mistake.”