Infectious disease complications occur when an infection leads to additional health issues beyond the initial illness. These complications can arise from the body's response to the infection or from the infection spreading to other parts of the body. Common examples include pneumonia following influenza or sepsis resulting from a bacterial infection. Complications can vary in severity and may require different treatments. Some complications can lead to long-term health problems or even be life-threatening. Early detection and appropriate medical care are essential to manage these complications effectively and improve patient outcomes.