Diseases that you can transmit by sexual contact are STDs. Contact may involve the mouth, penis, vagina or anus. Not everyone who has an STD has symptoms, so if you think it's possible that you may have contracted one, you should see a doctor for testing. Most STDs can be treated with antibiotics. Some are parasitic or viral, and require other treatment. The only way to be sure to avoid STDs is to avoid sex. Mutually monogamous relationships between uninfected partners is also safe. If neither of these practices is satisfactory, then limiting the number of partners, use of a condom where appropriate, and being choosy about partners may help limit your exposure. If you have an STD, the responsible thing to do is refrain from sex until your condition has been cleared up and your doctor or health care provider pronounces you safe. It's also responsible to let your partner(s) know they may have been exposed.