Leprosy, also known as Hansen’s disease, is a chronic infectious condition caused by the bacterium Mycobacterium leprae. This ancient disease continues to affect individuals worldwide, yet it is curable.
Current Global Landscape
Leprosy remains a health concern globally, with new cases detected annually. In 2023, 182,815 new cases were reported across 184 countries and territories, primarily from the WHO South-East Asia and African Regions.
While global prevalence has declined, some regions carry a disproportionate burden. For example, Brazil accounted for over 90% of the 24,773 new cases in the Americas in 2023. India reported approximately 107,000 cases in 2023, a 3.9% increase from 2022, and Southeast Asia contributed 79.3% of the global burden.
How Leprosy Spreads
Leprosy is caused by the slow-growing bacterium Mycobacterium leprae, primarily affecting the skin, peripheral nerves, and mucous membranes of the upper respiratory tract. While the exact transmission mechanism is not fully understood, it is believed to occur mainly through respiratory droplets from the nose and mouth of an untreated individual. Prolonged and close contact is generally required for transmission; casual interaction like shaking hands or sharing meals does not typically lead to infection.
Most people possess natural immunity to Mycobacterium leprae, with approximately 95% of those exposed not developing the disease. Genetic factors may play a role in susceptibility. Once a person with leprosy begins multi-drug therapy, they become non-infectious, usually within 72 hours.
Recognizing and Treating Leprosy
The signs and symptoms of leprosy develop slowly, often taking an average of five to seven years after infection to appear, though they can manifest within nine months or as long as 20 years. A common indicator is the presence of skin lesions that are paler or reddish and have a definite loss of sensation. Nerve damage is also a hallmark of the disease, leading to thickened or enlarged peripheral nerves, muscle weakness, especially in the hands and feet, and potential eye problems.
Diagnosis is primarily clinical, based on these cardinal signs. A skin smear test can also detect bacilli, helping to classify the type of leprosy. Leprosy is curable with multi-drug therapy (MDT), a combination of medicines that typically includes dapsone, rifampicin, and clofazimine. This treatment is provided free of cost globally by the World Health Organization (WHO) and has been supported by Novartis since 2000. Early diagnosis and prompt MDT can prevent disease progression and avoid permanent disabilities.
Addressing Misconceptions
Historically, leprosy has been associated with deep-seated misconceptions and social stigma. It is often mistakenly believed to be a curse or divine punishment, though it is a bacterial infection with no scientific basis for such beliefs. Another persistent myth is that leprosy causes body parts to fall off; in reality, the disease damages nerves, leading to a loss of sensation. This can result in unnoticed injuries and secondary infections if left untreated, potentially leading to deformities.
The stigma surrounding leprosy can significantly hinder early diagnosis and treatment, as individuals may delay seeking care to avoid social ostracism. Modern medical understanding and multi-drug therapy have transformed the outlook for affected individuals. With treatment, individuals are no longer contagious and can lead full, normal lives, underscoring the importance of education to dispel harmful misconceptions and promote acceptance.