Top 10 diseases facts

Syphilis was present in the Americas before European contact. It was carried from the Americas to Europe by the returning crewmen from Christopher Columbus's voyage. The first outbreak of syphilis in Europe occurred in 1494 in Naples, Italy, during a French invasion.

Sheep. Scrapie is infectious and incurable. Recent studies suggest prions may be spread through urine and persist in the environment for decades. Scrapie occurs in Europe and North America, but to date, Australia and New Zealand (both major sheep-producing countries) are scrapie-free.

Smallpox. After vaccination campaigns throughout the 19th and 20th centuries, the WHO certified the eradication of smallpox in 1979. The fact that humans are the only reservoir for smallpox infection, and that carriers did not exist, played a significant role in the eradication of smallpox. So far, it is the only eradicated infectious human disease.

Leprosy. Contrary to folklore, leprosy does not cause body parts to fall off. Infections, however, can result in tissue loss causing fingers and toes to become shortened and deformed, as cartilage is absorbed into the body.

Mercury poisoning. Mad hatter's disease is a common name for chronic mercury poisoning among hatmakers, who were often exposed to mercury vapors during felting works. Along with physical symptoms such as tremors or loss of hair and teeth, hatters tended to develop characteristic psychological traits, such as pathological shyness and marked irritability.

Poland. Historians aren't sure why Poland was spared the worst of the plague, even though all its neighbours got depopulated. It was the only place not affected by the disease on the European continent (Iceland was also spared because it was rarely visited and Black Death never reached there).

Rabies vaccine and sometimes rabies immunoglobulin are effective in preventing disease if given before the start of symptoms. However, only one person has survived a rabies infection without vaccination - it was Jeanna Giese, a teenager from Wisconsin. Unfortunately, the experimental treatment she had received didn't work for other patients.

Leprosy. Armadillos are a presumed vector and natural reservoir for leprosy in Texas and Louisiana. They must have acquired the disease from humans at some point, given that armadillos are native to the New World, where leprosy was unknown prior to the arrival of Europeans.

Overwork. Karōshi (過労死), which can be translated literally as "overwork death" in Japanese, is occupational sudden mortality. The major medical causes of karōshi deaths are heart attack and stroke due to stress and a starvation diet. This phenomenon is also widespread in other parts of Asia as well. The first case of karōshi was recorded in Japan in 1969.

Prion. A prion is composed of protein in a misfolded form. When a prion enters a healthy organism, it induces existing, properly folded proteins to convert into the disease-associated, prion form; the prion acts as a template to guide the misfolding of more proteins into prion form.