Deadly Prion Diseases Are Rising in the U.S., And We Aren't Exactly Sure Why

Imaging of the normal brain (left) and Creutzfeldt-Jakob disease (CJD; most common form of prion disease) with striking cortical ribboning.Photo byradiopedia.org (left) and Practical Neurology (right).

In the late 1980s, a mysterious and horrifying phenomenon occurred in Britain – over 120,000 cattle were dying from a fatal condition, dubbed "mad cow disease."

The alarm bells rang louder when it started infecting humans and manifesting as variant Creutzfeldt-Jakob disease (CJD), a highly fatal condition marked by rapid dementia, uncontrolled movements, and a brain resembling a spongy mess.

In response to this crisis, the US banned UK beef imports, a prohibition that lasted until 2020. But the truly perplexing aspect of this disease lay in its causative agent – not a bacterium, virus, or parasite, but a misfolded protein, known as a prion.

If you get prion disease, the chances of survival are almost 0%. About 85% of cases die within the first year of symptom onset. Prion disease is universally fatal because — unlike pathogens like bacteria and viruses —prions don’t get recognized by the immune system as a threat. So, prions inevitably degenerate neurons in the brain and kill the victim within a few years.

While variant CJD, linked to mad cow disease, is rare, a more common manifestation is sporadic CJD, accounting for 85% of prion-induced brain diseases. The origin of sporadic CJD remains unknown, but what's certain is its increasing occurrence.

A new study in JAMA Neurology, led by Dr. Matthew Crane at Hopkins, delves into this rising trend. Utilizing the CDC's WONDER database, which compiles cause-of-death data from death certificates, Dr. Crane's team observed a steady increase in CJD fatalities since 1990, alongside a rise in overall death and incidence rates:

Photo byCrane et al. (2023), JAMA Neurology

Photo byCrane et al. (2023), JAMA Neurology

This upward trend begs the question – why are prion diseases becoming more prevalent? Experts speculate there are three primary theories:

1. First, an aging population may be more susceptible to sporadic CJD.

2. Second, advancements in diagnostic techniques, like sophisticated MRI protocols and new tests like real-time quaking-induced conversion testing, have improved our ability to detect these diseases.

3. Third, and most ominously, could there be a new, unidentified exposure causing this increase?

While the study did not hint at which of these theories is most probably, the stark reality remains – prion diseases, though rare, are devastating and rising in the US for unclear reasons. This rise in cases underscores the need for heightened surveillance and research into these enigmatic and lethal diseases.