What are viral diseases? Viral diseases are extremely widespread infections caused by viruses, a type of microorganism. There are many types of viruses that cause a wide variety of viral diseases. The most common type of viral disease is the common cold, which is caused by a viral infection of the upper respiratory tract (nose and throat). Other common viral diseases include: Chickenpox Flu (influenza) Herpes Human immunodeficiency virus (HIV/AIDS) Human papillomavirus (HPV) Infectious mononucleosis Mumps, measles and rubella Shingles Viral gastroenteritis (stomach flu) Viral hepatitis Viral meningitis Viral pneumonia Viral diseases are contagious and spread from person to person when a virus enters the body and begins to multiply. Common ways that viruses spread from person to person include: Breathing in air-borne droplets contaminated with a virus Eating food or drinking water contaminated with a virus Having sexual contact with a person who is infected with a sexually transmitted virus Indirect transmission from person to person by a virus host, such as a mosquito, tick, or field mouse Touching surfaces or body fluids contaminated with a virus Viral diseases result in a wide variety of symptoms that vary in character and severity depending on the type of viral infection and other factors, including the person’s age and overall health. Common symptoms of viral diseases include flu-like symptoms and malaise. Viral diseases are not treatable with antibiotics, which can only cure bacterial diseases and infections. However, the most common viral diseases, the common cold and the flu, are self-limiting in generally healthy people. This means that the viral infection causes illness for a period of time, then it resolves and symptoms disappear as your immune system attacks the virus and your body recovers. In some cases, viral diseases can lead to serious, possibly life-threatening complications, such as dehydration, bacterial pneumonia, and other secondary bacterial infections. People at risk for complications include those who have a chronic disease or a suppressed or compromised immune system, and the very young and very old. In addition, certain types of sexually transmitted viral infections, such as HIV/AIDS and HPV, can lead to serious complications and death. Seek prompt medical care if you think you have a viral disease, especially if you are at risk for complications, or if you believe you have been exposed to a sexually transmitted disease. Seek immediate medical care (call 911) if you, or someone you are with, have serious symptoms of an illness or a viral disease, such as shortness of breath, chest pain, passing out (fainting), or a change in alertness or consciousness.