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A Social Issue Neglected Tropical Diseases and Three Major Infectious Diseases

Leprosy (Hansen’s Disease)

< Foot of a leprosy patient >

Mycobacterium leprae, a bacillus that mainly affects the skin, nerves, and mucous membranes, is the organism responsible for leprosy (also known as Hansen’s disease). Unless spotted and treated in its early stage, the disease may cause disfiguration of the face and limbs, affecting physical appearance. The number of reported cases have been declining globally. According to the World Health Organization's (WHO) official figures, there were 176,176 leprosy cases registered in 2015. In Japan, where leprosy is known as leper, the memory is still fresh in our minds of people being forcibly segregated in sanitariums.

Causes of Infection

Disease Agent

Mycobacterium leprae

< Microscopic view of Hansen’s bacillus on the skin from a leprosy patient > CDC

Reservoir Hosts

Rodents and nine-banded armadillos

Mycobacterium leprae grows on rodent footpads and inside the body of nine-banded armadillos. Although it is unknown how exactly the disease is transmitted, it is believed that the disease usually spreads in the form of respiratory droplets that travel from person to person in cases where an infected individual exhales, coughs, or sneezes in the immediate vicinity.
The bacteria that cause leprosy have low infectability and multiply very slowly (approximately every 13 days). It may take 2 to 10 years (or even 20 years) before signs and symptoms appear, which mostly affect the skin, nerves, and mucous membranes. It can cause disfigurement.


Leprosy is caused by bacterial infection and its effects can last over a long period. While the disease has a variety of symptoms, it mainly affects the skin, the peripheral nerves, mucosa of the upper respiratory tract, and the eyes. Patients can typically be classified into two groups: those with paucibacillary leprosy and those with multibacillary leprosy.

< Foot of a leprosy patient >

Paucibacillary leprosy

In the case of paucibacillary leprosy, the symptoms may be milder and are often characterized by hypopigmented skin macules (one or more) accompanied by loss of sensation or a reddish rash.

Multibacillary leprosy

The form of the disease known as multibacillary leprosy results in characteristically symmetric skin lesions (mostly pale red in color) in at least five locations as well as thickened dermis, nodules, plaques, and frequent involvement of the nasal mucosa, in turn resulting in nasal congestion and epistaxis. In some cases, these skin lesions might not exhibit loss of sensation.


Aside from the above symptoms, both paucibacillary leprosy and multibacillary leprosy can cause muscle decay, paralysis (particularly in limbs), eye disorders that could cause blindness, skin hypertrophy, and ulcers on the soles of the feet. If left untreated, this disease can cause nerve damage, leading to muscle weakness and atrophy, and permanent disability.

Diagnosis and Treatment

Early diagnosis and treatment can cure the disease completely.

Diagnostic Methods

WHO's(World Health Organization) Guide to Eliminate Leprosy as a Public Health Problem (1997) defines a case of leprosy as a person having one or more of the following, and who has yet to complete a full course of treatment:

  • hypopigmented or reddish skin lesion(s) with definite loss of sensation
  • thickening of the peripheral nerves, as demonstrated by loss of sensation and mobility of the hands, feet or face
  • positive skin smears.

Both paucibacillary leprosy and multibacillary leprosy can be treated with little difficulty through multidrug (dapsone, rifampicin and clofazimine) therapy (MDT) over 6–12 months.
Furthermore, this highly effective treatment has a low relapse rate and no known drug resistance has been reported to date. As with any medicine, however, some patients may have an allergic reaction to one or more of the drugs used in this treatment. In the majority of such cases, severe itching will occur accompanied by red or dark spots on the surface of the skin and the patient will be asked to cease MDT and referred to a hospital for observation.



To prevent leprosy and accompanying disabilities, it is essential to detect all cases as early as possible and to treat them with MDT.

Regions at High Risk of Infection

Worldwide, the number of cases is decreasing but there are pockets of high incidence in several countries, including India, Brazil, Indonesia, Angola, the Central African Republic, Congo, Madagascar, Mozambique, Nepal, Tanzania, and the Philippines. In particular, India has more than half of all reported cases, followed by Brazil and Indonesia.

Estimated Number of Infected People

According to data released from the Centers for Disease Control and Prevention (CDC) in 2010, worldwide 1 to 2 million people are permanently disabled by leprosy. While the number of new cases detected worldwide was 250,000 in 2008, the global registered prevalence of leprosy at the end of the first quarter of 2013 stood at some 190,000 cases, showing a clear declining trend. Of the 122 countries where leprosy had been a national problem in 1985, 119 countries have already eliminated this disease.

Estimated Number of the Deaths

While leprosy cannot be the direct cause of death, it leaves permanent disabilities when it is not properly treated or when the infection is not spotted early enough.

Initiatives by Pharmaceutical Companies and NGOs

Surprisingly, the history of leprosy in Japan goes back all the way to ancient times. Early references to leper (rai, leprosy in Japanese) can be found in literary works as far back as the Nihon Shoki (Written Chronicles of Japan, edited during the 8th century). Since its causes and treatment were unknown at that time and patients were left with conspicuous disabilities on the face and limbs, the disease has a long history of being considered a horrible disease in which sufferers were often ostracized by their communities and families.
It was only in the 1940s that the first breakthrough occurred: Dr. Guy Faget of the United States recognized the effectiveness of glucosulfone sodium, and its successor drug dapsone began to be used all over the world in the 1950s. However, the treatment took many years and, to make the situation worse, M. leprae started to develop resistance to dapsone in the 1960s. After lengthy research, a WHO research team established what is now called “multidrug therapy” (MDT) in 1981.
Since 1995, WHO provides free MDT for all patients worldwide, initially through a drug fund provided by the Nippon Foundation and, since 2000, through the MDT donation provided by Novartis. Additionally, a number of non-governmental organizations have helped to eliminate leprosy, including the International Federation of Anti-Leprosy Associations (ILEP), of which Japan’s Sasakawa Memorial Health Foundation is also a member.
In 2016 WHO launched a new global strategy – “The Global Leprosy Strategy 2016–2020: Accelerating towards a leprosy-free world” – which aims to reinvigorate efforts for leprosy control and to avoid disabilities, especially among children affected by the disease in endemic countries.


Novartis is providing the three drugs required for multidrug therapy (dapsone, rifampicin and clofazimine) free of charge through WHO until 2020. Aside from the donation of these drugs, Novartis undertakes wide-ranging activities in an effort to eliminate leprosy worldwide in cooperation with other organizations. In 2013 the Novartis Foundation launched a new leprosy strategy that focuses on interrupting transmission: early diagnosis and prompt treatment, contact tracing and prophylactic treatment of newly diagnosed patients, diagnostic tools to accelerate and/or objectivize diagnosis, and strict surveillance and response.

WHO- Neglected Tropical Diseases, accessed March 19, 2014,
CDC- Neglected Tropical Diseases, accessed March 19, 2014,