Mycobacterium Avium Complex (MAC) is a group of bacteria commonly found in the environment, particularly in soil and water. It includes species like Mycobacterium avium and Mycobacterium intracellulare. These bacteria can cause infections, especially in individuals with weakened immune systems, such as those with HIV/AIDS or other chronic illnesses. In healthy individuals, MAC usually does not cause disease. However, when it does lead to infection, symptoms may include fever, weight loss, and respiratory issues. Diagnosis typically involves laboratory tests, and treatment often requires a combination of antibiotics over an extended period.