How do you know if someone has hpv?

what are the symptoms, and why can't a condom protect you entirely from it?

Human papillomavirus (HPV) infection

Infection with the human papillomavirus (HPV) usually does not cause any symptoms and does not always produce visible genital warts.

When symptoms do develop, they usually occur 2 to 3 months after infection. However, symptoms have been known to develop from 3 weeks to many years after infection.

Symptoms that may occur with genital warts include:

Irritation.
Itching.
Bleeding.

HPV is spread by direct contact.
The virus can be spread to or from the genitals, anus, mouth, or throat during sexual activities. However, warts in the mouth or throat are extremely rare. Condoms may reduce the spread of infection, but they do not provide complete protection.
Once the infection occurs, it may spread to other areas of the genitals or to the anal area.
You can spread the virus even if you do not have any symptoms of infection or any visible warts.
A pregnant woman can infect her child during vaginal delivery, although this is very rare. The presence of genital warts does not mean that the mother should have a cesarean delivery, unless a vaginal delivery would cause the warts to bleed excessively

hope this helps...if you think you or someone you know may have this please be tested,
good luck

There are obvious visual symptoms and for a woman there may be some minor pain with a radical explosion but typically none. get a papsmere and it is a persons responsibility to tell another. Before you decide to have sex with someone , both of you get a check up. protect yourselves.
obgyn
They look like warts or tiny bumps. I believe condoms prevent the transmission of HPV so it might not be the actual intercourse that transmits it.
i.e. You touch someone in the infected genital area and then touch yourself. Or the other person touches himself (or herself) in the infected area and then touches you.
I believe that the foreplay may be transmitting it.
Most people who have a genital HPV infection do not know they are infected. The virus lives in the skin or mucous membranes and usually causes no symptoms. Some people get visible genital warts, or have pre-cancerous changes in the cervix, vulva, anus, or penis. Very rarely, HPV infection results in anal or genital cancers.

Genital warts usually appear as soft, moist, pink, or flesh-colored swellings, usually in the genital area. They can be raised or flat, single or multiple, small or large, and sometimes cauliflower shaped. They can appear on the vulva, in or around the vagina or anus, on the cervix, and on the penis, scrotum, groin, or thigh. After sexual contact with an infected person, warts may appear within weeks or months, or not at all.

Genital HPV is only transmitted through skin-to-skin contact during sex; infected skin of one-person rubs against the skin of the other person and transfers the virus. Almost all infections are acquired through vaginal or anal intercourse, but rarely HPV may be transmitted by oral-genital sex. The male condom is not as effective at preventing HPV transmission as it is for the prevention of other STDs; the male condom does not prevent all skin-to-skin contact during sex. The female condom provides wider coverage and therefore might offer greater protection.
Genital Warts:
Genital warts (also known as venereal warts) are caused by a virus, the human papillomavirus (HPV).
Warts are found on or around the penis, anus or vagina.
They are small lumps which have an irregular cauliflower-like surface.
The colour and shape vary depending on their location. Sometimes the warts cause irritation and itching.
Genital warts are a serious health concern as certain types of HPV have been associated with cervical cancer.
However, most women infected with genital warts do not have the strains of HPV that give rise to cervical cancer.
Genital warts often disappear even without treatment. However, there are a range of drug treatments.
Small warts can also be removed by freezing, burning or using laser treatment.
Occasionally, surgery is used to remove larger warts.
Condoms does not give 100% protection against STDs. Skin to skin contact in the pubic area is enough to transmit viral diseases among the partners.
Please see the webpages for more details and images on Human Papilloma Virus (Genital warts)
http://www.nlm.nih.gov/medlineplus/ency/...
http://en.wikipedia.org/wiki/genital_war...
http://news.bbc.co.uk/2/hi/health/medica...
http://images.google.co.in/images?svnum=...
http://images.google.co.in/images?q=huma...