Researchers work to combat rise in syphilis cases

In the U.S., syphilis is at its highest rate since 1950, with a nearly 80% increase since 2018, while babies born with syphilis have surged 937% in the past decade.

Symptoms of the sexually transmitted infection can include painless ulcers and sores that progress to body rashes on the palms and soles, hair loss, muscle pain and fatigue. Untreated, syphilis can cause blindness, deafness, paralysis and damage to the heart and brain.

Syphilis is easy to cure in the early stages with antibiotics like benzathine penicillin and doxycycline, said Dr. Arlene Seña, a researcher with the UNC Institute for Global Health and Infectious Diseases. But better diagnostics and a vaccine are urgently needed.

“Despite many advances in infectious diseases, we’re still using serological tests developed in the early 1900s to determine infection and response to therapy,” she said. “We also need a syphilis vaccine that can effectively prevent infections in those at risk for infection.”

Seña is leading a $1.9 million National Institutes of Health contract to develop a specimen biorepository, collecting clinical data and different sample types to advance syphilis diagnostics from patients at domestic and international sites like UNC Project Malawi. She also led the clinical project for a multicenter NIH grant to collect specimens for genomic sequence analyses and to identify future vaccine candidates.

“These are critical steps in the development of a syphilis vaccine with global efficacy,” she said.

Persistence of syphilis

Seña says the persistent and chronic nature of syphilis — an infection that can hide from the immune system and affect other organ systems if not treated — is fascinating. She educates healthcare providers about syphilis throughout the U.S. and is a consultant for the Centers for Disease Control and Prevention’s STI treatment guidelines on syphilis.

“Sir William Osler, the father of modern medicine, said that ‘those who understand syphilis understand medicine.’ This is a challenge for many clinicians that continues today,” she said.

Approximately 40% of babies born to women with untreated syphilis can be stillborn or die from the infection as a newborn. In 2012, there was only one case of congenital syphilis reported in North Carolina. In 2022, there were 55.

“Syphilis is one of the most difficult STIs to recognize and manage and can result in serious consequences in pregnant women if they are not screened properly,” Seña said.

Syphilis is caused by the Treponema pallidum bacterium, and research has been hindered because, until 2018, investigators were unable to successfully grow a long-lasting tissue culture of the bacterium. Testing is also complicated because the disease progresses into complex phases that can coexist with other STIs like genital herpes and HIV.

Currently, syphilis is diagnosed using a screening algorithm with serum antibody tests; however, these cannot reliably distinguish between current and past infections nor determine cure after antibiotics.