By Mariam Sunny

Nov 12 (Reuters) - The number of sexually transmitted infections $(STI)$ in the United States in 2023 was down nearly 2% from the year before, a sign the epidemic could be slowing, the Centers for Disease Control and Prevention said on Tuesday.

More than 2.4 million STIs were reported last year, compared to more than 2.5 million in 2022, with nearly half occurring in adolescents and young adults aged 15–24, according to a report by the agency.

The findings provide a "glimmer of hope" that the "tide is turning" after nearly two decades of increasing STI rates, Jonathan Mermin, Director of CDC's National Center for HIV, Viral Hepatitis, STD, and TB Prevention, said in a statement.

"It's been a long time since we have seen declines in STI rates, and so I am encouraged by this, but there's still a long way to go to... fully address the STI epidemic," said Laura Bachman of CDC's Division Of Sexually Transmitted Disease And Prevention.

Chlamydia was the most common nationally notifiable STI in the United States in 2023, with more than 1.6 million cases. That rate was similar to the previous year, but was 6.2% lower than the Chlamydia incidence in 2018.

Gonorrhea cases dropped 7.7% from 2022 to 2023, and fell below pre-pandemic levels.

The most infectious stages of syphilis, known as primary and secondary syphilis, decreased 10.7% in 2023, marking the first substantial decrease since 2001, the report said.

Increases in newborn syphilis, transmitted from mother-to-child during pregnancy, appear to be slowing in some areas, the CDC said. The number of cases rose 3% in 2023, compared to 30% annual increases in prior years.

Still, in 2023, more than a million more STIs were reported than in 2003, and nearly 4,000 babies were born with syphilis, the CDC said.

Data collection during the pandemic was difficult and potentially less reliable than usual, the CDC said.

Stigma is one of the biggest barriers to addressing the STI epidemic, potentially impacting individuals' willingness to be screened and providers' willingness to inquire about sexual history, Bachman said.

The epidemic disproportionately affects American Indian, African American, and Hispanic communities, as well as gay and bisexual men, the report said.

The agency said the improvements follow advancements in STI prevention, including use of antibiotics to prevent certain bacterial STIs and authorized at-home tests to detect the infection.

The U.S. Food and Drug Administration in August approved the first at-home, over-the-counter test to detect syphilis antibodies in human blood developed by privately held NOWDiagnostics.

(Reporting by Mariam Sunny in Bengaluru; Editing by Nancy Lapid and Shailesh Kuber)

((Mariam.ESunny@thomsonreuters.com;))