Sexually transmitted diseases (STDs) are infections that are passed from one person to another through sexual contact. The causes of STDs are bacteria, parasites, yeast, and viruses.  Sexually transmitted diseases (STDs) are caused by infections that are passed from one person to another during sexual contact. These infections often do not cause any symptoms. Medically, infections are only called diseases when they cause symptoms. That is why STDs are also called "sexually transmitted infections." But it’s very common for people to use the terms "sexually transmitted diseases" or "STDs," even when there are no signs of disease. There are many kinds of sexually transmitted diseases and infections. And they are very common — more than half of all of us will get one at some time in our lives. Use the list above to find out about each kind of STD.  This is an excellent book that offers practical information on the prevention, diagnosis and treatment of these infections, The sexually transmitted diseases source book offers more detail on individual disease, it is much more expensive and lacks this book's vital information about communication.