The most common way people are infected with HIV is by having sex with an infected person. You can't tell by looking at a person whether they have HIV, so you have to protect yourself -- and your sex partner.
and HIV Prevention
Don't have unprotected sex outside marriage or a committed relationship. If you or your partner has ever had unprotected sex -- or if either of you uses injected drugs -- the only way to be sure you don't have HIV is to get tested. Have two...
HIV is spread when blood,
semen, or vaginal fluids from an infected person enter
another person's body, usually through sexual contact, from sharing needles
when injecting drugs, or from mother to baby during birth.
WebMD Medical Reference from Healthwise
February 13, 2014
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