Name: Human Immunodeficiency Virus aka HIV

How You Get It: Unprotected sex leading to the transfer of bodily fluids, dirty needles, contact with infected blood, breast milk.

Gory Details: Like so many of the STDs we've discussed, HIV can seem like the flu. After that, there aren't necessarily "symptoms," but the virus weakens your immune system, leaving your susceptible to any number of bacteria, bugs and other baddies.

How You Kill It: There's no cure. And, no, there's no vaccine. If you're infected with HIV, however, there's a slew of antiviral drugs that can keep things in check. Many of these drugs have equally nasty side effects. You may have to try a bunch before you find the right one. And, when you do, it may not work forever. HIV's a pain in the ass, to be sure, so you should do everything in your power to prevent it. How? Condoms, condoms, condoms!