Sepsis occurs when the body's immune system has a dangerous and overwhelming response to an infection, leading to inflammation that can damage tissues and organs. It is caused by infections, most commonly bacterial, but can also be triggered by viral, fungal, or parasitic infections. The infection can start anywhere in the body, such as the lungs, urinary tract, skin, abdomen, or bloodstream. When the body's immune system overreacts to these infections, it can cause widespread inflammation, leading to organ dysfunction and potentially life-threatening complications. Sepsis is not contagious; it arises from an individual's own infection and immune response. Common infections leading to sepsis include pneumonia (lung infection), urinary tract infections, abdominal infections, skin infections, and bloodstream infections. People with weakened immune systems, chronic illnesses, very young or elderly individuals, and those with recent surgeries or wounds are at higher risk of developing sepsis.