THURSDAY, Feb. 14 (HealthDay News) -- Here's a new, and sobering, government statistic to ponder on Valentine's Day: More than 110 million men and women in the United States have a sexually transmitted infection.

In two studies published online Feb. 13 in the journal Sexually Transmitted Diseases, estimates of the prevalence and cost of treating STDs are tallied.

The numbers are not good.

One of the more concerning findings was that there are nearly 20 million new infections each year, and half of those occur among young people (aged 15 to 24).

And the cost of treating STDs is substantial: The lifetime cost of treating 20 million infections a year comes close to $16 billion, the report showed.

Eight STDs were included in the analysis, conducted by researchers at the U.S. Centers for Disease Control and Prevention. They included chlamydia, gonorrhea, hepatitis B virus (HBV), herpes simplex virus type 2 (HSV-2), HIV, human papillomavirus (HPV), syphilis and trichomoniasis.

Some of these infections can cause serious health problems that range from infertility to chronic pelvic pain and cervical cancer, the researchers noted. While women tend to suffer greater health consequences from STDs, just as many young men are infected as young women, the report showed.

"Sexually transmitted infections are a significant risk to people of any age who are sexually active, with some [infections] capable of transmitting through skin-to-skin contact," said Kaitlin Doyle, women's health coordinator at the Long Island Jewish Medical Center in New Hyde Park, N.Y. "We have to take measures to protect ourselves," she said.

Dr. Jill Rabin, head of urogynecology at Long Island Jewish Medical Center, agreed, adding that, "establishing an open and honest relationship with your physician or other health care provider is a very important first step. Screening today can be done with just a few easy tests, and to reduce risk always remember to use protection."

The findings highlight the need for greater prevention and screening efforts, and young people should be the first target of such efforts, the researchers noted.

Here are the current CDC screening recommendations for STDs:

Everyone should get at least one HIV test.

All sexually active women aged 25 and under, along with older women who have risk factors such as new or multiple sex partners, should be screened annually for chlamydia.

At-risk sexually active women should be screened annually for gonorrhea.

Pregnant women should be screened for syphilis, HIV, chlamydia and hepatitis B, while at-risk pregnant women should be screened for gonorrhea during their first prenatal visit.

All HIV-infected women should be screened yearly for trichomoniasis.

All sexually active gay and bisexual men should be screened at least once a year for syphilis, chlamydia, gonorrhea and HIV. Those who have multiple or anonymous partners should be screened more frequently for STDs (preferably three- to six-month intervals). In addition, those who also use illegal drugs, particularly methamphetamine, or whose partners use drugs should be screened more frequently.

More information

For more on sexually transmitted diseases, go to the U.S. National Library of Medicine.