Leprosy is a disease common in third world countries, where unsanitary conditions persist. It is caused by the bacterium Mycobacterium leprae, which was first seen under a microscope by Norway's Dr. Armauer Hansen in 1873. Prior to the discovery that the disease was caused by bacteria, people had thought that it was hereditary or even caused by sin.

Leprosy is often referred to as "the living death", since it can ravage the body and leave its victims deformed. It is a disease that attacks the central nervous system, allowing it to impact nearly all areas of the body indirectly. It is typically transmitted in airborne moisture droplets produced by coughing, breathing, and sneezing.

In the past, victims of leprosy were shunned by society and forced to form leper colonies. In these leper colonies, the infected lived an isolated life, sometimes with the help of outsiders. People developed many misconceptions about the disease, contributing to the highly negative conception of lepers.

Once the bacterium enters the body, it begins destroying the nerve endings, leading to a loss of feeling and pain. This loss of sensation causes the victim to endure injuries since they have no way of knowing that their tissues or bones are being damaged until it is too late. These injuries can lead to infection or other complicated conditions. Leprosy can also attack the mucous lining of the nose, causing it to collapse. Once the nerves behind the eye are destroyed, the victim loses ability to blink, causing their eyes to dry out.

The first semi-successful treatment for leprosy involved injecting patients with the oil of the chaulmoogra nut. This treatment began in the early 20th century, but was replaced in 1941 by the "promin" drug. The treatment was successful, but required excessive numbers of injections. During the 1950s, another treatment was developed by Dr. R.G. Cochrane in the form of dapsone pills. In the later half of the 20th century, the World Heath Organization began advocating a combination of different antibiotics to treat leprosy. This multi-drug therapy method has persisted to modern times and is considered the best method of treating the disease.

With the development of effective treatment techniques, the disease has become quite rare and leper colonies are uncommon. Scientists worldwide are still working to develop a vaccine for the disease, but funding is scarce since other diseases such as cancer and AIDS are more prevalent and deadly. Today, only 150 people a year are infected in the U.S., a much smaller number than other deadly bacterial diseases like tetanus and syphilis. Worldwide, the number is an average of 500,000 new leprosy cases a year.