Illnesses resulting from an infection are called infectious diseases. Infection is caused by the invasion of the tissues of an organism's body by disease-causing agents. Virus, bacteria, nematode, viroid, prion, etc. are some of the agents that cause infections. An infectious disease is caused when the host's protective immune mechanisms are weak. Microorganisms damage tissues by releasing several toxins or destructive enzymes. Persistent infection is a severe form of infection. It occurs when the body is unable to clear the organism after the initial infection. Use of anti-infective drugs is the most common way to treat infections. The topics included in this book on infectious diseases are of utmost significance and bound to provide incredible insights to readers. It explores all the important aspects of infectious diseases in the present day scenario. Those in search of information to further their knowledge will be greatly assisted by this book.