An STD/STI is contracted by unprotected sex with a potentially high-risk person, such as a new sexual partner, a stranger, or a partner who has multiple sexual partners.
The consistent use of barrier methods (such as condoms) can be an effective way to protect against STD/STI, but it is not 100% effective. Furthermore, many infections may be asymptomatic (i.e., have no symptoms) but the infected person is still infectious and can pass their infection to their sexual partners.
It is advisable to do testing:
• After casual sex with a stranger
• After ending a sexual relationship where the other partner was unfaithful
• If your partner tests positive for an STD/STI
• When starting a new sexual relationship or before starting unprotected sex in a new relationship
• When there are multiple sexual partners; at the minimum, yearly screening is recommended
• If symptoms of STD/STI are present (see below)
The most well-documented risks of transmission are: