In addition to the replies above which make some very could points, I thought I would add two things:
1) Some people who get HPV, and can pass HPV to others, will never show visible signs...even with the strains that produce warts. Some peoples' immune systems will keep the virus at bay. The warts are the result of a mutation in skin cells, from the virus infection. I've read numbers somewhere that something like 1 in 8 people who get HPV actually show visible symptoms EVER. (I don't know how accurate the number is, but a such number does exist to this fact)
2) It has HARD to get "tested" for HPV. The virus lies in the skin and not in the blood. Therefore, until you have visible symptons (ie warts), it is difficult to accurately test for HPV. When people go get checked, this usually does NOT include any form of a test for HPV. So, in most cases, people who say they have been tested.....are not necessarily clean of HPV.
I got tested multiple times before I knew I had HPV, and was told I was clean -- even when I'm positive now that I must have had it.
They really need to do a better job educating people about this virus in sex ed....I had never even heard of it or knew how contagious and common it was until it was too late.