Communicable, or infectious diseases, are caused by microorganisms such as bacteria, viruses, parasites and fungi that can be spread, directly or indirectly, from one person to another. Some are transmitted through bites from insects while others are caused by ingesting contaminated food or water. A variety of disease-producing bacteria and viruses are carried in the mouth, nose, throat and respiratory tract. Some communicable diseases such as ebola, enterovirus D68, flu, hantavirus, hepatitis A, hepatitis B, HIV/AIDS, measles, pertussis, rabies, sexually transmitted disease, shigellosis, and tuberculosis are discussed in this chapter along with their treatment in the table format.