"My father succumbed to Alzheimer's, and it was tough to deal with. The odd thing about this sort of disease is that the person effectively dies before their body does. So in the last five years he was alive, it was as if my dad was already gone, because he was. When he did pass away, it made the passing less traumatic, it was more of a relief in a way." - GotMyOrangeCrush

"If it ever made the jump to humans I would say CWD (chronic wasting disease). Symptoms don't show up until a couple years after infection but in that period of time the infected is highly infectious, it can be transmitted by bodily fluid contact, all the tissue of the infected is infectious and it can stay dormant in the environment for something like 10 years it can also be absorbed by plants and be transmitted if an animal were to eat the infected plants." - Lucite01

"Parkinsons. My dad is in late stages of Parkinsons and can no longer tell the difference between hallucinations and reality. Sometimes I wonder if some things he sees are really there and we can't see them because his mind works differently now. But other times, we know they are just hallucinations. Like him leaving and getting lost for hours. Or whatever. It's heartbreaking." - YEGMusic43

"Spongiform encephalitis, aka "Mad Cow" disease is pretty rough." - cmoellering "This brain disorder in adult cattle that may be spread to humans through diseased meat. Humans may acquire the disorder by eating diseased meat products. When it comes from cattle, the disorder is called Creutzfeldt-Jakob disease (CJD). CJD ultimately leads to dementia and death. The condition is rare. The disease is marked by rapid mental deterioration, usually within a few months. Most people eventually lapse into a coma." - Carry_fan1995

"Rabies. Get a shot within two days of being bitten or you will die from loosing your mind from extreme irrational fear." - GAZUAG

"Mine would be fatal familial Insomnia for sure. It starts with the victim just having regular trouble sleeping, then you become reliant on sleeping medication. Eventually they becomes ineffective and you're just tortured by tiredness. In the end, you just can't fall asleep. You basically exhaust yourself to death before you can sleep" - spikey_steve

"Flesh eating bacteria One day you're swimming in a pond and the next they're having to amputate limbs, like all of your limbs. https://abcnews.go.com/amp/Health/flesh-eating-bacteria-resulted-quadruple-amputation-reveals-deadlier/story?id=66934840 When a patient arrived at a hospital with necrotizing fasciitis, a flesh-eating infection, doctors did not know that the infection in question compromised multiple strains of bacteria. To save the patient's life, doctors had to perform a quadruple amputation." - GotMyOrangeCrush

"Resistant bacterial meningitis-you can be dead in less than 24hrs and it a horrible death." - trucorsair

"There's a disease that basically turns you into a statue, and during its progression, you must choose which position you want to be permanently stuck in." - NeedsMoreTuba

"Ebola" - bmbmwmfm , "All the hemorrhagic fevers are nightmare fuel." - dieinafirenazi

"Imo tuberculosis. It pretty much just slowly kills your organs one by one if it isn't stopped. Fortunately, there's a vaccine for it and antibiotics." - placeholderNull

"Creutzfeld-Jakob Disease (CJD), It's kind of the like the human equivalent of the Mad Cow disease, as it's a TSE. Proteins in your brain "unfold" and your brain practically disintegrates over the course of about 8 months. Symptoms are akin to Alzheimer's, but also include more physical symptoms such as myoclonus. Very scary." - JordieFinnie

"Fournier's Gangrene is an acute infection of the scrotum and penis. Full of tragic scrotum pain and redness with rapid progression. Would you mind not searching images for this? You'll be mentally scarred." - Carry_fan1995

"Between Alzheimer’s and cancer, not really much to choose. They are both just so unfathomably terrible. I’ve had loved ones with both, and can assure you all that they are truly awful." - beardedliberal

"I can't believe that SIDS wasn't mentioned yet. Nothing terrifies me more than sids. Go to check on your infant only to find them dead. Yes there's ways to reduce the risk, but it could still happen. (No I haven't lost one yet, and my heart screams for those that have. (I say yet because my youngest is nearing the 5 month mark.))" - Anuacyl