By Luke Langlois

If you live in constant fear of germs, diseases, amoeba, bacteria, viruses, or various disorders that can transform your internal organs into abstract artwork, this post may not be for you. We are extraordinarily lucky to have an immune system that can effectively ward off the literal gazillions of microscopic villains floating around the rock we call home. Furthermore, the researchers that have developed vaccines and other treatments galore have saved countless lives. But, there are some ailments that (for now) have quite simply stumped the human body. Here are a few of the diseases that have a greater than 99% case fatality rate (CFR), meaning that >99% of people diagnosed with a disease ultimately pass away during the disease. 

1. ~99% Case Fatality Rate – Balamuthia mandrillaris: First discovered in the brain of a mandrill in the San Diego Wild Animal Park (frighteningly close), the Balamuthia mandrillaris is a free-living amoeba that causes the lethal neurological condition known as granulomatous amoebic encephalitis. This infection causes necrosis (the injury and subsequent early death) in nervous system cells. While the disease can be difficult to diagnose due to its rare nature, symptoms include severe headaches, nausea, dizziness, irritability, and fever. As the disease progresses, seizures, loss of nerve function, and complete personality changes are common. Existing treatments are often experimental. The only two survivors of this disease suffer from permanent brain damage. In most instances of this disease, the victim had some sort of immunodeficiency.  
2. ~99% Case Fatality Rate – Naegleria fowleri: Typically found in natural (or poorly chlorinated) warm freshwater bodies, Naegleria fowleri is a eukaryote straight from your nightmares. Naegleria fowleri is colloquially known as the “brain-eating amoeba” because it travels up your nose and into your brain (by attaching itself to the olfactory nerve). There, it will travel through your brain as it pleases to feed on nerve tissue and rapidly reproduce. The overall condition is known as naegleriasis, or primary amoebic meningoencephalitis. Given its rarity, it is a difficult disease to diagnose, but symptoms include headache, fever, nausea, confusion, hallucination, ataxia (lack of voluntary muscle control), and seizures. Out of 450 documented naegleriasis cases, only seven people have survived. In general, it is a good idea to avoid submerging your head in untreated freshwater bodies. Also, chlorinate your pool!  
3. 100% Case Fatality Rate – Fibrodysplasia Ossificans Progressiva (FOP): This disorder is not a result of a microscopic horror. Rather, FOP is an incredibly rare genetic disorder of the body’s connective tissue. A mutation in the connective tissue’s repair and creation mechanism causes a body’s fibrous tissue to ossify, or turn into bone. Minor injuries can, for example, cause joints to become permanently frozen in place as bone comes into place of muscle tissue. Victims of this disorder are ultimately frozen as the “secondary skeleton” that forms becomes progressively restrictive. There is no cure or approved treatment for FOP, but research is underway. Affected people can live to be 40 years old if properly managed. As it is a genetic disorder, FOP is not contagious, but children of an FOP patient have a 50% chance of manifesting the disorder. 
4. 100% Case Fatality Rate – Transmissible spongiform encephalopathies: Rather than being one disease, transmissible spongiform encephalopathies are a group of 100% fatal diseases associated with prions, the most common being Creutzfeldt-Jakob disease. Prions are misfolded (thus ineffective) proteins in the brain that have the ability to project this shape onto other proteins in the brain, causing an exponentially growing infection. Unlike viruses or bacteria, prions are virtually indestructible. Symptoms include dementia, personality changes, hallucinations, psychosis, and myoclonus (abrupt or jerky muscle movements). Variants of prion diseases can be genetic, but the primary disease, Creutzfeldt-Jakob, is contagious if one were to come in contact with an infected brain. Transmission is not yet understood completely, but know that prion diseases are extraordinarily rare, and universally fatal. 

In conclusion, we are fragile mortals. Appreciate your life! 

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Health and Disease Editor: James Zheng