Viral diseases are extremely widespread infections caused by viruses, Viruses are very tiny organisms with their diameters in nanometers level and exist almost everywhere, such like in the air, soil and animal body. There are many types of viruses that cause a wide variety of viral diseases. The most common viral disease are Chickenpox, Flu (influenza), Herpes Human immunodeficiency virus (HIV/AIDS), Dengue Fever, Hepatitis A, B, Human papillomavirus (HPV), Infectious mononucleosis, Viral Gastroenteritis, Mumps measles and rubella, Shingles, Viral gastroenteritis (stomach flu), Viral hepatitis, Viral meningitis and Viral pneumonia. Viral diseases are contagious and spread from person to person when a virus enters the body and begins to multiply. Human immune system can generate antibodies against viruses, the antibody will recognize the virus and destroy it.