The diseases caused by germs and which may infect any part of the body are called Infectious Diseases. They can spread by any means where there is a germ. They are caused by pathogenic microorganisms such as bacteria, virus and fungi. Germs can be spread by direct or indirect contact. Vaccination, Maintenance of Proper Hygiene and Medicines help in the prevention of infection. Infectious diseases have a range of causes, and they can be found all over the world. These diseases are considered contagious or communicable, meaning that they can be passed from person to person. Therapy or treatment is the attempted remediation of a health problem, usually following a diagnosis. Clinical Infectious diseases are caused by microorganisms like fungi, bacteria, viruses and even parasites. They are contagious and transmitted by insects, animals and by taking contaminated food and water. Chickenpox, measles, typhoid are some of the infectious diseases. Some of the infectious diseases also lead to cancer such as Human papillomavirus causes cervical cancer; lymphoma is caused by infection of Epstein-Barr virus. These infectious diseases are clinically diagnosed by laboratory tests such as blood tests, urine tests, lumbar puncture, throat swabs, computerized tomography, magnetic resonance imaging and biopsies studies.