How worried should you be about getting herpes? The unfortunate answer is “probably more than you are”… and this may be true even for those who are in a long-term relationship.

Unsettling new data reveals that one out of six Americans between the ages of 14 and 49 is infected with herpes simplex virus type 2 (HSV-2). This is a lifelong, incurable infection that can cause recurring and painful genital sores in men and women. Why have we been unaware that the numbers are so high? Because the symptoms often arise sporadically… can be very mild or mistaken for something else… and some people have no symptoms at all. For all of these reasons, an estimated 90% of those infected never even know that they have the infection — not to mention that they don’t realize that they are capable of infecting others as well.

These high infection rates were revealed in the National Health and Nutrition Examination Survey, based on interviews and blood samples taken between 2005 and 2008. I contacted Scott Bryan, spokesperson for the federal Centers for Disease Control and Prevention office for HIV/AIDS, viral hepatitis, STDs and tuberculosis, to learn more.

Bryan told me that HSV-2 infection is nearly twice as prevalent among women (20.9%) as men (11.5 %). He explained that the reason behind the gender discrepancy is that during intercourse, genital tissue in women is more easily abraded, and abrasions make it easier for the virus to enter the body. Also, women’s genitals have more moist tissue, the kind that is most susceptible to HSV-2 infection.

All this adds up to the unwelcome news that herpes is far more common than most people realize, even today when we’re presumably aware of the need to take measures to protect ourselves from sexually transmitted diseases. I thought it worth revisiting the appropriate strategies for staying safe — and for avoiding spreading the disease if you or your partner is already infected.

If You Have No Herpes Symptoms…

Your best bet is to use common sense and take measures to avoid getting herpes in the first place. Ask your doctor whether you should be tested for herpes — the answer is probably yes if you haven’t had a blood test, don’t know whether you have, or if you have had one or more new partners since last being tested. If results show that you’re in the clear — great! Though it may seem obvious, it bears emphasizing that you should absolutely not have sex with anyone who has visible open sores on the genitals, thighs or buttocks. Beyond that, if you don’t know for certain that your relationship is exclusive or that you’re both infection-free, you’re safest if you use condoms for intercourse and a mouth dam for oral sex.

If You Know You Have Herpes…

Tell your sexual partner. Whether or not you have symptoms and whether or not your partner has developed the infection, honesty is the best policy. Protective measures include consistent and correct use of condoms and refraining from sex while you have visible sores. Both strategies dramatically reduce the risk of transmission.

You may have also seen ads for the prescription drug valacyclovir (Valtrex), which not only reduces symptoms but also cuts the risk of transmission by about half… but only if it is taken immediately upon noticing symptoms (for each outbreak) and continued daily till they’re gone. There can be side effects, unfortunately, and they’re unpleasant — including headache, upset stomach, vomiting, diarrhea, constipation and, more seriously, rash, itching, confusion, yellow skin or eyes, fever and blood in the urine. Valtrex should not be taken if you have a compromised immune system .

The best advice is old-fashioned, I’m afraid. To avoid catching herpes and spreading it, a mutually exclusive, long-term relationship is the surest bet.

You can get more information on herpes infection and how to live with the disease on the Web site of the American Social Health Association (www.ashastd.org).