Federal officials note that sexual activity among younger people has decreased. That might in part explain the drop in the herpes rate.

Sexually transmitted diseases (STDs) are on the rise across the United States, with the rates of chlamydia, gonorrhea, and syphilis increasing in frequency since 2014.

At the same time, fewer young people are having sex than in years past, which may be causing the rate of herpes infection to drop.

While it might be difficult to understand why these two seemingly contradictory trends are taking place at the same time, they shine a light on several aspects of sexual health.

Dr. Jose Bazan, DO, an infectious disease physician at the Ohio State University Wexner Medical Center and medical director of the sexual health clinic at Columbus Public Health, told Healthline that while the herpes decline is welcomed news, the rise of other STDs is of great concern.

“Definitely, the alarms are sounding and from a public health perspective — providers like us that work in this field and see a lot of these patients — we recognize that this is a big problem,” he said.

A recent report from the Centers for Disease Control and Prevention (CDC) found that the prevalence of herpes has gone down.

Two forms of the herpes simplex virus — HSV-1, which causes cold sores, and HSV-2, which is also known as genital herpes — have seen declines in the past two decades.

About 48 percent of Americans between the ages of 14 and 49 had HSV-1, and 12 percent had HSV-2 in 2015–2016. The rates in 1999–2000 were 59 percent and 18 percent, respectively.

“I don’t think we know all the exact reasons as of yet, but some of the explanations that have been mentioned include safer sex and younger individuals waiting until they’re older before they start engaging in sexual practices,” said Bazan. “I don’t think we really know all the reasons, but ultimately that is good news.”

Indeed, the CDC reported last month that fewer high school students are having sex than in years past.

According to the survey data, in 2015 about 41 percent of high school students reported that they’d had sex — down from 47 percent in 2005.

These numbers are in line with recent numbers showing that teen birth rates hit a record low in 2017.

The decline in sexual activity might explain in part why the herpes rate has dropped, but it wouldn’t account for why the other sexually transmitted diseases are on the rise.

In addition, hypodermic needles aren’t a factor. While contaminated needles can transmit diseases such as hepatitis and HIV, they can’t transmit STDs.

The CDC reports that the more than 2 million cases of chlamydia, gonorrhea, and syphilis reported in the United States in 2016 represent a record high.

In fact, between 2015 and 2016, syphilis rates increased by nearly 18 percent.

All three STDs can be treated with antibiotics, but in some cases — especially with gonorrhea — antibiotic-resistant strains can be difficult to treat.

Young women are disproportionately affected by chlamydia, accounting for nearly half of all diagnosed infections.

Syphilis, meanwhile, tends to affect men who have sex with men.

“When you look at the individuals that are being affected by these three STDs, you’re looking at young, sexually active adults, but also minority populations — ethnic and racial minorities, along with the gay and bisexual population,” said Bazan.

“So I think a big thing to keep in mind is that a lot of these patient populations may not have ready access to care — and when you don’t have ready access to care, populations like that get disproportionately affected by conditions such as STDs, unfortunately,” Bazan added. “Some of these patient populations are not readily or consistently engaged in care and it may be because of a lack of access, and we really need to bring them in.”

Among men who have sex with men who have been diagnosed with syphilis, about half are also living with HIV.

The CDC report emphasizes that this data shows the importance of integrating STD and HIV prevention and care services.

Compounding the issues caused by syphilis is the fact that the infection can be passed on from mothers to babies. Between 2015 and 2016, the rate of newborns with syphilis increased by 28 percent.

While there’s no definitive answer as to why herpes rates are declining while other STDs are reaching epidemic levels, the medical community is sounding the alarm.

The CDC report calls for renewed commitment on three fronts.

They stated that health departments at the state and local levels need to have adequate infrastructure for detecting and treating STDs.

They also state that healthcare providers should focus on STD screening and treatment.

Finally, they state that everyone should talk openly about STDs, get tested regularly, and practice safe sex.

Bazan agrees with these recommendations, pointing out the less obvious ways that STDs can affect the population.

“On an individual level, they can cause psychological stress and trauma,” he said. “They can also propagate HIV, which is another concern. They can be associated with negative reproductive health. They can damage the reproductive tract in women.”

“Obviously, the trend is concerning,” he concluded. “What it tells us is that we really need to focus on the patient populations that are really being disproportionately affected by STDs, and we really need to double down and allocate public health resources in order to reach out to them and engage them in care.”