Washington (AFP) - Sexually transmitted diseases surged to a record high in the United States last year, with more than two million cases of chlamydia, gonorrhea and syphilis nationwide, officials said Tuesday.

This was "the highest number ever," said the annual Sexually Transmitted Disease Surveillance Report released today by the US Centers for Disease Control and Prevention (CDC).

Most of the new cases -- 1.6 million in 2016 -- involved chlamydia, a bacterial infection that affects both men and women.

Gonorrhea also increased among men and women last year, but the steepest rise was among men (22 percent), said the report.

Nationwide, gonorrhea cases reached 470,000, with a large share of new gonorrhea cases among men who have sex with men.

These trends are "particularly alarming" because of the growing threat of gonorrhea becoming resistant to the last recommended treatment, according to the CDC report.

Syphilis cases numbered 28,000, a rate that increased nearly 18 percent from 2015 to 2016.

Most cases of syphilis occur among men -- mainly gay, bisexual and other men who have sex with men.

But women too saw a 36 percent increase in rates of syphilis.

There were more than 600 cases of syphilis among newborns -- known as congenital syphilis -- a 28 percent increase in a single year.

These syphilis cases led to "more than 40 deaths and severe health complications among newborns," said the report.

"Every baby born with syphilis represents a tragic systems failure," said Gail Bolan, director of CDC's Division of STD Prevention.

"All it takes is a simple STD test and antibiotic treatment to prevent this enormous heartache and help assure a healthy start for the next generation of Americans."

Experts say despite growing concerns about antibiotic resistance, these three STDs can all be cured with antibiotic treatment.

If left untreated, however, they can lead to infertility, life-threatening ectopic pregnancy, stillbirth in infants, and increased risk for HIV transmission.

"Increases in STDs are a clear warning of a growing threat," said Jonathan Mermin, director of CDC's National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention.

"STDs are a persistent enemy, growing in number, and outpacing our ability to respond."