Infections or diseases that are transmitted through sexual intercourse are called sexually transmitted infections (STIs) or sexually transmitted diseases (STDs). This happens when a healthy person have unprotected sex with infected person.
The organisms (bacteria, viruses or parasites) that cause sexually transmitted diseases may pass from person to person in blood, semen, vaginal and other bodily fluids.
The common symptoms of STDs include clear, white, greenish or yellowish vaginal discharge, discharge from the penis, strong vaginal odor, vaginal itching or irritation, itching or irritation inside the penis, pain during sexual intercourse and painful urination.
STDs are caused by different types of pathogens :
![](https://df0b18phdhzpx.cloudfront.net/ckeditor_assets/pictures/1297071/original_List_of_pathogens.png)
Thus, out of all the diseases mentioned above, three diseases gonorrhea, syphilis and chlamydiasis are caused by bacteria.