The United States is experiencing a "steep and sustained" spike in sexually transmitted diseases, a new government analysis shows.

Cases of gonorrhea, syphilis and chlamydia all increased in 2017, making it the fourth straight year in which STD infections continued to rise.

"The United States continues to have the highest STD rates in the industrialized world," said David Harvey, executive director of the National Coalition of STD Directors. "We are in the midst of an absolute STD public health crisis in this country. It's a crisis that has been in the making for years."

Concerns are also mounting that gonorrhea could soon become resistant to all current antibiotics, officials from the U.S. Centers for Disease Control said.

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More than 4 percent of gonorrhea samples now are resistant to azithromycin (Zithromax), one of two antibiotics now used to cure the bacterial infection, the CDC says. That's up from 1 percent in 2013.

"The finding adds to the complexities of gonorrhea treatment," said Dr. Gail Bolan, director of the CDC's Division of STD Prevention. "Our nation must plan for the future. Our nation urgently needs additional treatment options for gonorrhea."

CDC records show that in 2017:

Gonorrhea cases increased 67 percent, rising from 333,004 to 555,608 diagnoses. Infections among men nearly doubled, and cases among women increased for the third year in a row.

Syphilis diagnoses increased 76 percent, from 17,375 cases to 30,664 cases. Nearly 7 in 10 infections occurred among men who are gay or bisexual.

Chlamydia remained the most common STD with more than 1.7 million cases diagnosed, up from around 1.6 million the year before. About 45 percent of cases were among young women aged 15 to 24.

"After decades of declining STDs, in recent years we've been sliding backwards," Bolan said.

These STDs are curable with antibiotics, yet most cases go undiagnosed and untreated, according to the CDC.

If untreated, these diseases can affect a couple's ability to get pregnant, cause ectopic pregnancy and stillbirth, promote chronic pain in the pelvis or abdomen, and increase a person's risk of contracting or transmitting HIV, the CDC noted.

New sex ed guidelines

Experts at the 2018 STD Prevention Conference, where the new CDC numbers were presented in a Tuesday media briefing, chalk rising STD rates up to several factors. The conference is taking place in Washington, D.C.

There's not enough screening for sexually transmitted diseases, particularly among young people who are most vulnerable, Harvey said.

"Doctors are not screening and testing for STDs, and patients don't know they need to ask for that screening and treatment," he said at the briefing.

A lack of sex education also is contributing to the spread of STDs, said Michael Fraser, executive director for the Association of State and Territorial Health Officials.

"There's really good science out there. There's ways to do effective programs based on evidence and data," Frazer said at the briefing. "Certainly, there's a lot more we could do."

Finally, the experts said that funding for public health response to STDs has diminished over the years.

"The explosion in STDs comes on the heels of years of cutbacks in federal funding," Harvey said. "Federal STD funding has seen a 40 percent decrease in purchasing power since 2003. That means state and local health departments are working with budgets that are effectively half what they were 15 years ago."

Over the years, gonorrhea has become resistant to nearly every class of antibiotics used against it. Ceftriaxone (Rocephin) now stands as the only antibiotic to retain high effectiveness against gonorrhea in the United States, the CDC says.

In 2015, the CDC began recommending that gonorrhea be treated with a single shot of ceftriaxone accompanied by an oral dose of azithromycin. Azithromycin was added to help delay the development of resistance to ceftriaxone.

This strategy has warded off resistance to ceftriaxone, the CDC says. There has not yet been a confirmed treatment failure with the dual therapy.

But gonorrhea appears to be developing new resistance against azithromycin, raising concerns that the dual therapy approach could crumble in the future.

Experts are worried that azithromycin-resistant genes in some gonorrhea strains could cross over into gonorrhea that is not as susceptible to ceftriaxone. If that happens, a strain of gonorrhea could someday surface that would be resistant to ceftriaxone.

The CDC is urging doctors to stem the spread of STDs by promoting frank discussion of the infections, testing patients for STDs and promptly treating any cases they find.