Leprosy, also known as Hansen’s Disease is a chronic,mildly communicable disease caused by infection from Mycobacterium leprae, a rod-shaped, acid-fast bacillus. It primarily affects the skin; the mucous membranes, especially those in the nose; and the peripheral nervous system.

Leprosy exacts a high physical and social toll. If left untreated, it can result in deformity and disability. In many societies, people with leprosy have been made outcasts from their communities.

The Norwegian doctor, Gerhard Armauer Hansen first observed M. leprae as an acid-fast, alcohol-fast, strong Gram-positive bacillus in tissue specimens from leprosy patients in 1873. The following year, he proposed that the bacteria caused leprosy; hence the name 'Hansen's Disease' emerged.

M. leprae infection occurs primarily in human beings. Researchers do not know exactly how the bacteria are transmitted. For many years, leprosy was believed to be transmitted through skin-to-skin contact. However, experts now consider this unlikely because M. leprae are not usually found on the skin’s surface. Most evidence suggests that people become infected by inhaling the bacteria. With each cough or sneeze of an untreated Person With Leprosy (PWL), the bacilli are discharged as droplets. Prolonged, close contact with infectious persons is likely to increase the risk of transmission.

When the National Leprosy Control Program (NLCP) was established in 1986, there were 38,570 registered leprosy patients in the country.  That number translated into a Prevalence Rate (PR) of 7.2 per 10,000 Filipinos.

By the end of 1998, with 7,005 registered patients and a PR of 0.90 per 10,000 population, leprosy was no longer considered as a public health problem by both the Department of Health (DOH) and the World Health Organization (WHO).

In 2004, the number was further reduced to 3,149 registered cases and a PR of 0.38 per 10,000 population.