Cases have risen by 80 percent since 2018, the C.D.C. reported. But chlamydia remains far more common.
Syphilis, once nearly eliminated in the United States, continues to resurge, reaching the highest rate of new infections recorded since 1950, the Centers for Disease Control and Prevention said on Tuesday.
More than 207,000 cases were diagnosed in 2022, the last year for which data are available. That represents an 80 percent increase since 2018, and 17 percent over the previous year’s tally, according to a new C.D.C. report.
The rates soared in every age group, including newborns. In November, the C.D.C. said more than 3,700 cases of congenital syphilis were reported in 2022, roughly 11 times the number recorded a decade ago. The disease caused 231 stillbirths and 51 infant deaths in 2022.
Experts pointed to a slew of reasons for the continued increases in syphilis and other S.T.I.s.
Substance use, which is tied to risky sexual behavior, has risen. With better prevention and treatment for H.I.V., condom use has fallen out of vogue — decreasing by about 8 percentage points between 2011 and 2021 among high school students, for example.