A disease is a condition that affects the normal functioning of the body or mind. It can be caused by various factors, including germs like bacteria and viruses, genetic issues, or environmental influences. Common examples of diseases include the flu, diabetes, and heart disease. When someone has a disease, they may experience symptoms such as pain, fatigue, or changes in mood. Preventing and treating diseases often involves a combination of healthy habits and medical care. Regular check-ups with a doctor, a balanced diet, and exercise can help keep the body strong. Vaccines are also important in preventing certain diseases, like measles and influenza.