The incidence of chlamydia, gonorrhea and syphilis is increasing, according to a new report from the Centers for Disease Control and Prevention. An estimated 110 million Americans now are infected with a sexually transmitted disease.
Chlamydia is the most common S.T.D., and the number of cases rose 4.7 percent from 2015 to 2016. The increases occurred nationwide; rates were highest in the South and lowest in the Northeast.
Chlamydia is usually asymptomatic, and the number of reported cases may have grown in part because of newer, more sensitive screening techniques.
Adolescents and young adult women have the highest rates of chlamydia: one survey found that 9.2 percent of girls aged 15 to 19 were infected, as were 8.0 percent of women aged 20 to 24.
Rates declined 3.5 percent among African-Americans and 6.4 percent among Native Americans and Alaska Natives, but chlamydia still is most common in these groups. Rates rose among all other races and ethnicities.
From 2015 to 2016, gonorrhea infections increased 22.2 percent among men and 13.8 percent among women, the C.D.C. reported. Almost 92 percent of cases are in people 15 to 44 years old.
The only recommended treatment is to take two antibiotics simultaneously, ceftriaxone and azithromycin. Resistance to azithromycin is becoming more common, however, and there is some evidence of growing resistance to ceftriaxone, as well.
“Several drug trials are going on now that we hope will provide new treatments for gonorrhea,” said Dr. Gail Bolan, the director of sexually transmitted disease prevention at the C.D.C.
“But these treatment trials take years, and we don’t know if these new drugs will be safe and effective.”
The rate of primary and secondary syphilis in 2016 is the highest it has been since 1993, and it increased among both men and women from 2015 to 2016. Men account for almost 90 percent of cases, and most are among men who have sex with men.
Rates of syphilis increased in every age group and all races, and they were highest among people in their twenties. The number of babies born infected with syphilis increased to 628 cases in 2016, from 492 in 2015 — each case, in Dr. Bolan’s words, “a needless tragedy.”
”The enormity of the S.T.D. epidemic requires everyone play a role in reversing these trends,” Dr. Bolan said.