what causes leprosy

Leprosy, also known as Hansen's disease, is caused by long-term infection with the bacteria Mycobacterium leprae or Mycobacterium lepromatosis. These bacteria primarily infect the skin and peripheral nerves. The bacteria have a slow growth rate and are obligate intracellular pathogens, meaning they cannot grow outside host tissues. Transmission occurs mainly through prolonged close contact with an infected person, likely via respiratory droplets when the infected person coughs or sneezes. The bacteria may also spread through contact with fluid from the nose of an infected person. Casual contact such as shaking hands or sitting next to someone with leprosy does not generally cause transmission. Not everyone exposed to the bacteria develops leprosy; about 95% of people who are exposed do not develop the disease. Factors that increase the risk of developing leprosy include prolonged contact with someone infected, living in poverty, and conditions that reduce immune function like malnutrition. Genetic factors also play a role in susceptibility to the disease. Leprosy causes nerve damage due to both direct bacterial invasion and the body's immune response, leading to symptoms like numbness, muscle weakness, and skin sores. In summary, leprosy is caused by Mycobacterium leprae or Mycobacterium lepromatosis bacteria, which spread primarily through respiratory droplets during extended close contact with an infected person. Genetic and immune factors affect disease susceptibility and progression. Early diagnosis and treatment can prevent severe complications.