(06-21) 15:39 PDT SAN FRANCISCO -- Since the AIDS epidemic, awareness of sexually transmitted diseases seems embedded as a Bay Area cultural norm. Yet most people don't know about how common viral STDs actually are.

Experts say being exposed to at least one STD virus is virtually inevitable. Viral STDs make up the modern "4-H club." Herpes simplex virus (HSV), human papilloma virus (HPV), hepatitis (B and C), and HIV are the most common STDs, causing pain, cancer, liver disease and AIDS, respectively.

Condoms significantly decrease transmission rates of the most life-threatening viruses, HIV and hep B and C. But it's not foolproof - statistics on liver disease show that 60 percent of hepatitis carriers acquired the virus by means other than sexual intercourse, such as recreational IV drug use or by receiving a tainted blood transfusion.

But for those 40 percent, a latex condom would have prevented transmission. As long as there is no breakage or leakage, using latex condoms for all sexual penetration prevents transmission of both hepatitis and HIV because those viruses are transmitted through body fluids. Condoms also prevent female-to-male transmission of those viruses.

To be considered safe sex, disease prevention needs to be at the 99 percent level. With the correct use of an intact condom, this is possible for HIV and hepatitis viruses.

Unfortunately, condoms do not do an adequate job of protecting against human papilloma or herpes simplex virus infections. Women diagnosed with HPV are often mystified and frustrated, having been "super careful," or picky, in choosing intimate partners and faithfully using condoms for all intercourse.

But UCSF researchers have shown these viruses to be present on genital skin with no symptoms that might prompt diagnosis and treatment. That means HPV and HSV can be deposited on the condom's outer surface from viral particles living on the scrotum, penile shaft not covered by the condom or vaginal/vulvar tissues.

Photo: Courtesy Of Dr. Ricki Pollycove, See Above

Women become aware they have HPV because they see some wart-like bumps in the vaginal area or it is found during annual exams. Screening with Pap smears, including newer viral DNA testing, allows for more accurate and sensitive identification of those women who are at significantly elevated risk for cancer because of having acquired high-risk subtypes of HPV.

Unless men identify a genital wart, they are not aware of harboring HPV, as we don't do Pap smears on men. Outside of research trials, we don't detect male high-risk HPV carriers.

Passing a virus without having any symptoms is why these viruses get spread far and wide. Like bees sharing pollen flower to flower, men regularly transmit HPV and HSV without knowing it.

Women can also pass viruses without having any symptoms. But female-to-male infectivity is estimated at less than 5 percent of the rates of male-to-female transmission.

In 2011, a panel of the Centers for Disease Control and Prevention recommended boys, as well as girls, be immunized for HPV. (To prevent cervical cancer, HPV immunization is recommended for all girls before becoming sexually active, ages 10 to 26, for several years now.)

Lowering the risks of human papilloma virus through immunization and preventive measures will thwart thousands of cervical, anal and oral cancers. Herpes simplex virus, as unpleasant and complex as it can be, does not cause cancer, and there are good antiviral medications to shorten painful episodes and prevent recurrences.

HIV and hepatitis B and C are well controlled with condom use. Yet if we acquire a lifelong viral "souvenir" through sex, may it be from a person who is important forever. It's a minimal-regrets way to assess the value of a relationship before risking exposure. When it comes to viral STDs, the devil is in the details.

Since it appeared in print, this column has been corrected to accurately reflect which agency recommended HPV vaccines for boys.