Cases of three common sexually transmitted diseases in the U.S. reached a record level in 2018, according to a new report from the Centers for Disease Control and Prevention.

Gonorrhea and cases of primary and secondary syphilis – the disease's most infectious stages – both reached their highest levels since 1991 last year. The country's 115,045 syphilis cases included more than 35,000 cases of primary and secondary syphilis, marking a 14.9% rate uptick from 2017. Meanwhile, there were more than 583,000 cases of gonorrhea, a rate increase of 5% from 2017, and the rate of reported chlamydia cases rose 3% to total more than 1.7 million in 2018 – nearly two-thirds of which were among people 15 to 24 years old, the report shows.

Together, the diseases accounted for more than 2.4 million cases – an all-time high since data on all three conditions was first collected in 1984.

Syphilis, gonorrhea and chlamydia can have serious consequences if left unchecked, including infertility and death, but are treatable through antibiotics. Yet despite public health efforts to improve access to testing and treatment, the prevalence of such STDs has soared in recent years, representing "an underestimated opponent in the public health battle," according to the report.

"We are not keeping up on the resurgence of (sexually transmitted infections) in this country," says Dr. Gail Bolan, director of the CDC's Division of STD Prevention. "Timely detection followed by timely treatment is our main strategy to treat individuals to improve their own health and to reduce transmission in a given community. Clearly, transmission is outpacing our detection and treatment efforts at the moment."

Officials pointed to a combination of factors that appear linked to the increase in STDs, including social factors that can affect access to health care – like stigma, drug use, poverty and unstable housing – as well as risky sexual behavior and slashed funding for STD programs across the country.

Bolan says increased and improved testing contributes to the higher numbers in recent years, but can't completely explain the growth.

"The situation is multifactorial – there's not one simple explanation for why we're seeing the significant increases every year," she says. "The good news is that we're actually doing a better job of documenting cases and understanding what the missed opportunities are in those cases, so we can focus on interventions to close those gaps."

Some of those missed opportunities are in prenatal care for pregnant women, Bolan says. The report notes a 39.7% year-over-year surge in the rate of congenital syphilis , which occurs when a mother passes the infection to her baby during pregnancy and can cause infant death and serious health issues. There were 94 infant deaths and stillbirths tied to syphilis last year, according to the report.

Although 41 states reported 1,306 cases of congenital syphilis in 2018, 70% were concentrated in just five states: Texas, California, Florida, Arizona and Louisiana. The uptick is tied to higher rates of syphilis overall in those states, as well as a nationwide rate increase among women – 172.7% in primary and secondary syphilis between 2014 and 2018.

Health officials are "trying to stay ahead of the curve" to prevent states with fewer congenital syphilis cases from seeing a surge, Bolan says. Helping women seek prenatal care early in pregnancy, and ensuring that their doctors are screening for syphilis and linking infected women to treatment would help prevent transmission, she says. Pregnant women who don't have syphilis but may be at higher risk of infection, such as those who live in areas with a concentration of syphilis, should be tested again in the third trimester.

"A number of women have been referred to other clinics in the area for treatment and have been lost to follow-up," Bolan says. "We want to make sure that these women are actually linked to treatment, and the treatment is documented so that we can prevent congenital syphilis."

Despite the recent increases among women, men who have sex with men saw the highest share of primary and secondary syphilis cases in 2018. But the report notes that rates of syphilis, chlamydia and gonorrhea rose among both males and females, all racial and ethnic groups and across the U.S., and that sustained efforts among public health and health care systems are needed to curb the rates.