Mycobacterium avium is a type of bacteria that belongs to the Mycobacterium genus. It is commonly found in soil, water, and dust, and can also be present in domestic and wild birds. This bacterium is known to cause infections, particularly in individuals with weakened immune systems, such as those with HIV/AIDS or other immunocompromising conditions. In healthy individuals, Mycobacterium avium typically does not cause disease. However, when it does lead to infection, it can result in symptoms like fever, weight loss, and respiratory issues. Treatment usually involves a combination of antibiotics, but it can be challenging due to the bacterium's resistance to many common medications.