The number of sexually transmitted diseases in the United States is hitting record highs, according to latest data from the Centers for Disease Control and Prevention (CDC).

Nearly 2.3 million cases of chlamydia, gonorrhea and syphilis were diagnosed in 2017, says the CDC. This is the fourth year of increases in STDs and the figures broke 2016's record by more than 200,000 cases.

Chlamydia remained the most common condition reported to the CDC. More than 1.7 million cases were diagnosed in 2017, with 45 percent among 15- to 24-year-old females.

Chlamydia, gonorrhea, and syphilis often go undiagnosed and untreated, leading to conditions including infertility, ectopic pregnancy, stillbirth in infants, and increased HIV risk.

“We are sliding backward,” said Dr. Jonathan Mermin, director of the CDC's National Center for HIV/AIDS, Viral Hepatitis, STD and TB Prevention, in a news release. “It is evident the systems that identify, treat and ultimately prevent STDs are strained to [a] near-breaking point.

"Diagnosed cases of gonorrhea increased 67 percent from 333,004 to 555,608 cases, and nearly doubled among men, from 169,130 cases to 322,169 in preliminary data for 2017. Diagnosed cases among women increased for the third year in a row from 197,499 to 232,587.

Syphilis diagnoses increased 76 percent, from 17,375 to 30,644 cases. Gay, bisexual and other men who have sex with men made up almost 70 percent of primary and secondary syphilis cases where the gender of the sex partner is known in 2017. Primary and secondary syphilis are the most infectious stages of the disease.

Researchers say the increases in STDs can be attributed to socioeconomic factors like poverty, stigma, discrimination, and drug use.

While most of the diseases are curable with antibiotics, gonorrhea continues to be resistant to nearly every class of antibiotics used to treat it, with the exception of ceftriaxone.

In 2015, the drug azithromycin was added to treatment for gonorrhea to help delay resistance to ceftriaxone. New CDC findings show that emerging resistance to azithromycin is on the rise in laboratory testing.

“We expect gonorrhea will eventually wear down our last highly effective antibiotic, and additional treatment options are urgently needed,” said Gail Bolan, M.D., director of the CDC's Division of STD Prevention in a press release. “We can’t let our defenses down — we must continue reinforcing efforts to rapidly detect and prevent resistance as long as possible.”