The diseases which are caused by pathogenic microorganisms, such as bacteria, viruses, fungi and parasites are known as infectious diseases. These diseases can invade the body and disrupt its normal functioning. Infectious diseases can range from common infections like the flu or a cold to more severe conditions such as tuberculosis, HIV/AIDS, malaria, and hepatitis. The diagnosis of infectious diseases begins with a thorough medical history and physical examination. This includes a study of the patient's symptoms, duration of illness, recent travel history, exposure to sick individuals and any underlying medical conditions. Imaging studies, such as X-rays, computed tomography (CT), and magnetic resonance imaging (MRI) are used to determine the extent and severity of certain infectious diseases, particularly those affecting the lungs, bones, or central nervous system. This book includes some of the vital pieces of work being conducted across the world, on various topics related to infectious diseases. It will provide comprehensive knowledge to the readers.