STI Cases Rebound in 2021, With Syphilis Surging 32% to Levels Not Seen Since 1950

The Centers for Disease Control and Prevention released its latest sexually transmitted infection surveillance report on a Tuesday in April 2023, and the numbers for 2021 were hard to read as anything but a rebound. After a slight dip in the first year of the pandemic, combined cases of chlamydia, gonorrhea and syphilis rose 6%, to more than 2.53 million reported cases. That puts the country close to its pre-pandemic high of 2.55 million. In 2020, the total had been about 2.39 million.

Syphilis drove the steepest climb. Cases jumped 32%, from nearly 134,000 in 2020 to nearly 177,000 in 2021. Chlamydia rose about 4%, to 1.64 million cases, and gonorrhea also rose about 4%, to 710,000. The report found that STIs continue to disproportionately affect gay and bisexual men, younger people, Black Americans and American Indian and Alaska Native people.

Dr. Leandro Mena, who directs the CDC's Division of STD Prevention, summed up the findings by saying the report shows STIs have no sign of slowing down. The report does have limits. It covers only the infections providers are required to report to health departments: chlamydia, gonorrhea and syphilis. HIV is also reportable but gets its own report. Left out are HPV and trichomonas, a parasite that CDC data estimate caused 2.6 million infections in 2018. Dr. Ina Park, a professor of family and community medicine at the University of California, San Francisco, said the report shows only a very small slice of the pie of what is happening with STIs in the United States.

The 2020 dip, according to the report, came from fewer chlamydia cases. Chlamydia counts rose in 2021 but have not returned to pre-pandemic levels. Park said that likely reflects lower screening rather than less infection, since people were not routinely getting tested. Chlamydia, particularly in women, is almost always asymptomatic, so a missed screening often means a missed case.

Park called the syphilis surge the most disturbing part of the report. The infection can be treated easily with antibiotics, and it had fallen to a low of around 31,000 cases in 2000. It has since grown nearly sixfold, to almost 177,000 cases in 2021. The last year cases exceeded that figure was 1950.

The human cost is sharpest for babies. Syphilis can be deadly for infants born to mothers who have it. Park called congenital syphilis a preventable tragedy and said the country needs a robust public health response, because there is no reason a baby should die of it in 2023.

Experts cited several factors behind rising rates: declining condom use, limited access to health care and increased substance abuse. David Harvey, executive director of the National Coalition of STD Directors, warned that with no new federal investment in STI prevention and a lack of federal leadership, the rates will keep rising. His group is asking for more than $300 million in additional funding for the CDC's Division of STD Prevention, along with a national strategy from the Biden administration and support for the state and local public health workforce to expand testing and treatment.

Mena pointed to reducing the stigma around STI testing and widening access to it. He also noted that recent data suggest that for high-risk groups, including men who have sex with men, taking the antibiotic doxycycline after sex can lower the risk of infection. What to watch now is whether the funding and national strategy advocates are seeking materialize, and whether screening recovers enough to show the true size of the problem.