This document discusses communicable diseases, which are diseases that can be transmitted from one person to another. It provides examples of common communicable diseases like the cold, flu, pneumonia, hepatitis, mononucleosis, sexually transmitted diseases, and HIV/AIDS. It then explains different modes of transmission for communicable diseases, such as direct contact, vectors/reservoirs, airborne transmission, food/water, and indirect contact. The rest of the document delves into more details about specific diseases, their symptoms, treatments, and methods of prevention.