Despite all the safe sex messages, there has been little progress in stemming the spread of sexually transmitted diseases in the United States.
STDs like chlamydia and herpes are more common than ever, and doctors are now starting to see a couple of new or previously unrecognized infections.
"The overwhelming concern is that STDs continue to be epidemic and that some of the infections are increasing," says Julius Schachter, editor of the journal Sexually Transmitted Diseases and a professor of laboratory medicine at the University of California, San Francisco.
There are an estimated 19 million new cases of STDs each year in the United States, up from 15 million nearly a decade ago. Experts don't have exact numbers because not all diseases are reported to the Centers for Disease Control and Prevention in Atlanta and many people don't know they're infected.
Among the most shocking estimates are that one in five Americans has genital herpes and more than half of women will contract HPV, or human papillomavirus, which causes genital warts and can lead to cervical cancer. At least a million Americans are living with the deadly AIDS virus.
STDs can cause lesions, discharge and other symptoms, but oftentimes they are "silent" and show no outward signs.
That's frequently the case with chlamydia. Just over 877,000 cases were reported in 2003, yet it's estimated there are 2.8 million new cases annually.
There are some signs of progress. While chlamydia and HPV cases are rising, some of the increase is due to better testing and detection, experts say. Gonorrhea cases are at an all-time low, though they are increasing among gay men.
In addition, scientists are working to create vaccines that would prevent HIV and HPV. Researchers are reporting tremendous success with the HPV vaccine, which could become available within a few years. Work also is under way on microbicides, which are creams or gels that a woman would apply to her vagina to protect against STDs, but progress has been slow on this front.
In the dark about STDs
Think you're not at risk for a sexually transmitted disease? So do many people, which is precisely the problem. In fact, most people who transmit STDs aren't aware of it, experts say.
"One of the great misconceptions is that people who have STDs know they have them," says Dr. Edward Hook, a spokesperson for the American Social Health Association and a professor of medicine at the University of Alabama at Birmingham. "That is absolutely incorrect."
Don't miss these Health stories
More women opting for preventive mastectomy - but should they be?
Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.
- Larry Page's damaged vocal cords: Treatment comes with trade-offs
- Report questioning salt guidelines riles heart experts
- CDC: 2012 was deadliest year for West Nile in US
- What stresses moms most? Themselves, survey says
- More women opting for preventive mastectomy - but should they be?
The solution: get tested — regularly if you have multiple sex partners. But discussions about STDs are too often missing during routine check-ups.
"Both doctors and patients are waiting for the other person to raise the subject and as a result nobody talks about it," says Hook.
If you don't know you're infected, you can't have an informed discussion with a potential partner. But frank talk about STDs among sexual partners also is much too infrequent.
Results of the Zogby/MSNBC.com online survey on sexuality found that just 39 percent of respondents always asked whether a prospective partner was infected with HIV or other STDs.
Hook isn't surprised. "People don't want to conceptualize themselves as being at risk," he says. People tend to think, "I'm not that kind of person and since I'm not, I wouldn't hang out with that kind of person," he says.
"There's just a disconnect," says Dr. Richard Sweet, director of the Women's Center for Health at the University of California at Davis and a spokesperson for the American College of Obstetricians and Gynecologists.
And many of those most at risk — teens and young adults — think they are invincible, according to Sweet. "A 16-year-old guy — he's a superhero," he says.
But the failure to come to grips with the threat of STDs is a major problem in the United States. "We have the highest rates of STDs in the industrialized world," Sweet adds.
The health consequences can be significant.
"STDs are taking a tremendous toll on American health," says Jessica Frickey, an HIV and STD specialist at the CDC.
In women, chlamydia can lead to pelvic inflammatory disease and eventually to blocked Fallopian tubes and infertility. But a woman may not know she's been infected until she has trouble conceiving and doctors explore why.
The most worrisome STD, of course, is HIV, because it can be fatal. Particularly troubling is the emergence over the last several years of strains of the virus that are resistant to some of the available medications aimed at keeping the virus under control. "It's certain that the virus is very clever and it changes," says Schachter.
Diseases under the radar
And some STDs have largely flown under the radar of doctors. One, called lymphogranuloma venereum, or LGV, is a form of chlamydia that has been recently detected among homosexual men, though there's evidence it's been in the United States as far back as the 1930s.
"It's not new," says Schachter, "we just haven't looked for it" until now.
Homosexual men infected with LGV may experience anal ulcers and bleeding, swollen lymph nodes, fever, chills and weight loss. "They're pretty sick," says Schachter.
The disease responds to antibiotics but the concern is that because the disease causes open lesions, it could spread more easily and, even worse, facilitate the spread of HIV.
Currently, the disease is most commonly seen in gay men in the United States, but Schachter expects it to spread to more women since some gay men are bisexual. Symptoms in women include vaginal lesions and swollen lymph nodes.
Meanwhile, Hook says herpes is being "reconceptualized." While it was once believed that infected people could only transmit the virus when they had visible blisters, doctors now know there is viral shedding even when there are no apparent symptoms — and the virus is actually often spread during these periods. That's a major concern since only one in 10 infected people are aware they have it, says Hook.
Another concern is a bacterial infection called mycoplasma genitalium, which has been emerging over the last decade. It's known to cause inflammation of the urethra in men but doctors know little more about its effects, let alone who's most at risk for contracting it.
Experts say the best ways to protect yourself against STDs are to limit your number of sexual partners and always use condoms, a practice that Hook says is "still woefully uncommon." But even with correct condom use, diseases like herpes and HPV can be transmitted because they appear on skin surrounding the genitalia.
That's why it's vitally important for partners to talk with each other about their sexual history and get tested regularly if they're at risk.
One of the major barriers to preventing STDs is simply convincing Americans to pay attention to their sexual health, according to Hook.
"I think the progress against STDs has been modest at best," he says, "and that will continue to be the case until we can resolve the American paradox in which sex and sexuality pervade nearly every part of society, the entertainment and media, but when it comes to our own health we don't want to address the problem."
© 2013 msnbc.com