Public health officials throughout Southern California are grappling with alarming increases in syphilis, gonorrhea and chlamydia that are part of a national epidemic.

In 2015, total combined cases of the three sexually transmitted diseases reached an all-time high, according to a late 2016 report by the Centers for Disease Control and Prevention. The report noted that gonorrhea rates were at historic lows and syphilis was close to elimination earlier in the 2000s but now the STDs pose “a substantial health challenge.”

Last year’s data is not yet available, but for Los Angeles County, which has some of the higher rates in the state, from 2011 to 2015, reported cases of gonorrhea were up 75 percent. Syphilis jumped by 80 percent and chlamydia increased by 14 percent, according to figures from the California Department of Public Health.

The reasons are complex, but include medical and social factors ranging from a lack of adequate screening to decreased fear of curable sexually transmitted diseases.

“No one really knows the definitive cause of all this,” Ried said. “No one can pin it on one or two things.”

In neighboring counties, STD cases have likewise jumped significantly.

In Orange County, the most recent data shows a 412 percent increase in syphilis cases from 2011 to 2016, a 204 percent increase in gonorrhea, and a 59 percent increase in chlamydia, said Dr. Christopher Ried, medical director of STD/HIV for the county Health Care Agency.

In San Bernardino County, between 2011 and 2015, reported gonorrhea cases increased by 96 percent, syphilis by 137 percent and chlamydia by 2.5 percent.

For Riverside County, between 2011 and 2015, reported gonorrhea cases were up 142 percent, syphilis 74 percent and chlamydia 12 percent.

The CDC says with most STD cases going undiagnosed and untreated, people are at “risk for severe and often irreversible health consequences,” including infertility, chronic pain and increased transmission of HIV. Treating STDs costs roughly $16 billion annually.

In California, the highest STD rates are found among young people, African-Americans and gay and bisexual men, according to the state.

SCREENING GUIDELINES

The CDC recommends the following screening guidelines:

• Sexually active women under 25, or older women with new or multiple sex partners, should be tested annually for chlamydia and gonorrhea.

• Pregnant women should be tested for syphilis and chlamydia early in pregnancy.

• Sexually active gay and bisexual men should be tested for syphilis, chlamydia, gonorrhea and HIV at least once a year, more frequently for those with multiple or anonymous partners.

Dr. Jennefer Russo, medical director for Planned Parenthood of Orange and San Bernardino Counties, said each year the group performs more than 180,000 exams and 170,000 STD tests. She said when seeing patients, clinic staff tailor their messages specifically to individuals.

“Just saying you should use a condom is not as effective as saying, ‘How often are you using a condom?’ and if it’s not all the time, asking, ‘What gets in the way of that?’” Russo said.

Community groups have developed strategies to target at-risk populations.

In Los Angeles, LA Condom distributes more than 2 million free condoms each year at 500 locations ranging from tattoo parlors to gyms to restaurants.

In San Bernardino County, Planned Parenthood runs two programs with outreach not only to schools, but group homes and foster care agencies, said Amy Streavel, director of community education and outreach.

“A lot of the time they don’t know that being under 18 they have access to reproductive health services,” Streavel said.

STARTING IN SCHOOLS

In Santa Ana, the nonprofit Orange County Bar Foundation offers comprehensive sex education to middle and high school students through the after-school Cuídate program. Nazly Restrepo, director of the program, said teens learn how to use condoms and skills such as refusing sexual contact.

“I really think a lot of it is lack of knowledge,” Restrepo said. “If they’re not getting it at school or at home where are they going to get this information? We still get red in the face when we talk about penises and vaginas.”

In Orange County, teens and young women ages 15 to 24 have the highest rates of chlamydia. Men 20 to 34 have the highest rates of gonorrhea.

Restrepo said research from the national Cuídate program shows that teens who participate delay the onset of sexual activity, which is contrary to fears that teaching youth about sex amounts to giving them permission.

“The brain isn’t developed just yet. That’s why kids just do things and don’t think,” she said. “It’s just a risky age, period. It helps them stop and think and that’s really critical.”

Ried said on the medical side, factors contributing to the rise in STDs include lack of testing and diagnosis in asymptomatic patients. He said high-risk gay and bisexual men should be screened every three months. Relying only on urine screenings, without culture swabs, will miss large numbers of chlamydia and gonorrhea infections of the throat and rectum.

For syphilis, cases among pregnant women are of urgent concern because the disease can be fatal to their babies. Last year, 15 infants were born with congenital syphilis in Orange County, Reid said.

“It really looks like it’s all about prenatal care,” he said, regarding prevention.

WHAT ELSE IS BEING DONE

Ried said Orange County, this year, will participate in a study that could boost the number of screenings by eventually allowing patients to swab their own genitals and avoid appointment wait times.

“Studies have shown when patients collect their own swabs they do just as good a job as doctors,” he said.

He also said most doctors are not using a state law that allows them to prescribe extra medication that a patient can give to his or her sexual partners who may be unwilling to come in for an appointment.

“It works really well to decrease the recurrence rate,” Ried said. “It’s very under-utilized.”

Among social factors, Ried said the fear of unprotected sex or multiple partners during the 1980s and 1990s was driven by seeing people dying of AIDS. But now advances in treatment can control HIV.

“No one sees these sick people and worries about it,” he said. “I think there’s a lot more cavalier behavior when it comes to sex. There’s definitely a lack of worry out there which contributes to more STDs.”