Although it was once very common, smallpox is now considered to be one of the most rare diseases, and it only exists in scientific laboratories. Kuru, another rare disease, can only be contracted by eating the flesh of another human being, particularly a member of the Fore tribe of New Guinea. Hutchinson-Gilford progeria causes a handful of children in the world to age rapidly, and Fields disease is named after twins who are the only known sufferers of the muscle-deteriorating disease.
Smallpox, now one of the rarest diseases, was caused by the variola virus. This virus caused a number of symptoms, including fevers and muscle aches. A rash that covered the entire body, however, was the most noticeable symptom of this disease. This rash typically consisted of fluid-filled pustules. When these broke open, they usually caused scars.
Today, smallpox is considered one of the most rare diseases in the world, though this was not always the case. Millions of people have died from this disease in the past, but contracting smallpox is now almost unheard of. By the 1980s, the World Health Organization declared that this disease had become eradicated from the earth thanks to vaccines. Small amounts of this virus still exist, however, in a few government laboratories across the globe.
Kuru is a prion disease similar to mad cow disease and its human counterpart, Creutzfeldt-Jakob disease. This disease affects a person's nervous system, and it is characterized by symptoms such as trembling and difficulty swallowing. Eventually, sufferers of this disease slip into a coma and die.
Most people will never be at risk of contracting this disease, since it is one of the world's most rare diseases. It primarily afflicted members of the Fore tribe in the highlands of New Guinea. After a serious epidemic in the middle of the 20th century, scientists discovered that this disease can only be contracted by eating the brains of a member of this tribe. Once the members of this tribe were educated regarding this discovery, the disease nearly disappeared.
Hutchinson-Gilford progeria is another one of the world's most rare diseases. This is a rare genetic disease in which a child appears to age very rapidly. Scientists estimate that only one out of eight million infants will be born with this disease.
Symptoms usually begin to present themselves in the toddler years, and they can include stunted growth, hair loss, organ failure, wrinkled skin, arthritis, and other medical problems typically common in elderly people. Sufferers of this disease also typically have small faces and pinched noses. Most patients with progeria will only live until their teens, but some may survive into their 20s.
With only two documented cases in the world, Fields disease is often considered to not only be one of the most rare diseases, but the most rare disease in the world. This condition was named after two Welsh twins, Kirstie and Catherine Fields. This disease caused their muscles to start deteriorating at around age four. By the time they were nine years old, the girls began relying on walkers and wheelchairs to get around. Since their diagnosis, doctors have found no other cases of this disease.