Immorality is the cause of 100% of all STD transmission

Think about it.

To get an STD, you have to have sex with an infected person. If you aren't married, your sexual act itself is immoral. If you are married, then you can't get an STD unless one of you has sex with someone else. The person had sex with someone other than their spouse. Even if the spouse was okay with the extra-marital sexual encounter, the sex act was immoral. If you only just got married, and one of you has an STD, they must have gotten the STD from pre-marital sex, an immoral act.

Even a doctor or nurse who contracts the disease from an infected person, or a nun who gets the disease from an infected blood transfusion, or a lifeguard gets it by giving mouth to mouth resuscitation, all of these cases the moral person gets the disease from an immoral person. The individual transmitting the disease first must get the disease. And they had to have got it from immoral activity, sexual activity. Sex within marriage is not immoral. But if they are married, they got the STD from their spouse. And where did the spouse get the disease? By having sex with someone ELSE? Well that's cheating, which is definitely immoral. If the spouse got it before they got married, well, the spouse had to have had sex before marriage. And pre-marital sex is immoral.

Even single people who have monogamous sex with their boyfriend or girlfriend... uh... premarital sex is immoral. No matter how you slice it, all STD transmission involves at least one immoral person, and most often two people doing an immoral sexual act.

So if you are worried about STDs, avoid immoral people.