You acquire STDs via sexual contact. Genital herpes, for example, is only contracted when a susceptible person (that is, has never had the infection before and thus isn't making antibodies against the virus) has intimate contact with a person that not only has the infection, but is also actively shedding the virus, which then enters the susceptible patient via mucus membranes or abraded skin (hence the areas these infections occur -- mouth, genitals and anus). As for other STDs, sexual contact is also necessary to expose the bacteria/viruses to epithelial linings that they can infect.

Yes, they can be transferred sexually (which is the main way), but there are still other ways. HIV/AIDS is considered an STD. It can also be transferred through blood, breast milk, and other body fluids. Genital herpes is also an STD, but since a girl didn't have sex to get it, she must've gotten it another way.

Vertical transmission of STDs doesn't typically cause the symptoms most people associate with STDs. Yes, you are correct that HIV can be passed parenterally, via breast milk, etc. But this is a poor example because HIV selectively affects CD4 T cells and not epithelial tissue associated with the genitals -- rather this virus causes reactivation of latent viruses if already present. On the other hand, you do not pass genital herpes on to a fetus during delivery. You can pass the virus (herpes simplex 2) to a neonate, but it will not cause genital vesiculations/nodules/papules or other genital symptoms (because the virus isn't exposed to this area). They may present with other symptoms such as encephalitis. Thus, genital herpes is only acquired via horizontal transfer, sexually. Other STDs, say gonnorhhea and chlamydia, are also passed to the neonate during delivery, but again, they do not display the typical manifestations that are associated with STD infections, but rather usually an ocular manifestation such as conjunctivitis. Again, to display genital manifestations of an infection, it is acquired via sexual contact.

Wow, that was a lot to take in.

Must say, really good explanation and thanks for the information doctor or whatever you are.

STI. they aren't really called std's anymore

Ok, that makes sense.

I believe it is also possible to test negative for certain STD's (HIV mostly) until several months after exposure. So, I agree that she may not necessarily have cheated.

90 There are STI's but they're a bit different from STD's.

A reasonable explanation? What did he slip and fall into her ******?

Also, "awkward"? I don't think it means what you think it means.

that's not reasonable for the op

It's a smart idea before having any kind of sex. Condoms don't prevent everything.

Apparently, she's loose enough all by herself.

32 - the point of couples getting tested for stds when they start dating is usually so they can start having unprotected sex (we dont know if shes on the pill or wanted babies). if she tested clean then theres no reason so think she will infect him, but she cheated. DUH!

Hate to break it to you, #32, but you can still get STDs while using a condom. And it's also possible to get pregnant while using one, it's not 100%. There are a lot of things that can go wrong.