What are the common symptoms of STIs?

STIs can cause physical symptoms like bumps or sores on the skin, itchy discharge, pain or burning during urination, fever, or symptoms like the flu. But all of these symptoms can be caused by other illnesses that are not sexually transmitted. Some STIs do not cause any symptoms at all. So, you can see how difficult it would be to diagnose a STI just based on symptoms you may be experiencing.