Various diseases can affect the human body, ranging from infections to chronic conditions. For example, diabetes is a chronic disease that affects how the body processes glucose, leading to high blood sugar levels. Infections like the flu or COVID-19 are caused by viruses and can spread easily from person to person, often resulting in respiratory symptoms. Other diseases, such as heart disease, involve the heart and blood vessels, potentially leading to serious complications like heart attacks. Cancer is another significant disease, characterized by the uncontrolled growth of abnormal cells in the body. Understanding these diseases is crucial for prevention and treatment.