Your health depends on physical, mental, and social well-being, while illnesses affect the body's organs. General practitioners and medical specialists can help treat common and specific illnesses respectively in hospitals, clinics, or through tests and treatments. Infectious diseases are caused by microorganisms like bacteria, viruses, protozoa, and fungi that can be transmitted between people or animals and may be prevented through vaccination or healthy habits like handwashing; non-infectious diseases have other causes like genetics, injury, or lifestyle and can be prevented by a balanced lifestyle with diet, exercise, and stress management.