Syphilis is one of many sexually transmitted infections. A sexually transmitted infection (STI)is an infection caused by a pathogen that spreads mainly through sexual contact. This generally involves ...Syphilis is one of many sexually transmitted infections. A sexually transmitted infection (STI)is an infection caused by a pathogen that spreads mainly through sexual contact. This generally involves direct contact between mucous membranes or their secretions. To be considered an STI, an infection must have only a small chance of spreading naturally in other ways.
