For some, the world suddenly goes blurry. Others describe it as having a dust storm in your eyes, or being shaken up in a snow globe. People might see flashing lights or black spots drifting through their field of vision, or acquire a sudden sensitivity to light, worse than walking into the sunlight after having your eyes dilated. If patients aren’t treated, some will inevitably go blind.
Many medical providers never suspect the culprit: syphilis. Usually, a syphilis infection shows up first as a firm, painless sore on the genitals or inside the mouth or anus, then as a rash, often on the hands and feet. If the infection is caught in either of these two stages, the cure is a shot of penicillin, which kills the bacteria. Left untreated, syphilis can enter another, more dangerous phase, attacking the heart, bones, brain, or nerves years or even decades later. Only about 1 to 5 percent of syphilis cases are thought to involve the eyes.
But now, eye symptoms are showing up seemingly all by themselves. Last year, doctors reported 17 new cases of eye syphilis to the Chicago Department of Public Health, mostly in people assigned male at birth with no other signs of the disease. In southwest Michigan, in 2022, five women showed up at clinics with ocular syphilis that ended up being traced back to the same male partner. Experts are disturbed by what these cases might portend: that syphilis has been allowed to spread so widely, and for so long, that what used to be considered a fringe event might not be so rare anymore.
Because eye-syphilis symptoms can be the only noticeable sign of the disease, by the time people do get correctly diagnosed, their vision might be permanently damaged. Peter Leone, an infectious-disease physician at the University of North Carolina School of Medicine, is haunted by a patient who came into his hospital in 2015. The 33-year-old man had been experiencing blurred vision, light sensitivity, and ringing in his ears for weeks, but was misdiagnosed with a sinus issue at the emergency room and sent home with antibiotics. By the time Leone saw him two weeks later, the man could barely count the fingers on a hand held directly in front of his face. Leone immediately began treating him for syphilis, but he never regained his vision.
“Obviously it’s disturbing,” Leone told me. Eye syphilis “was a rare event before, and there seems to be a resurgence.” He was so troubled by the patient he saw in 2015 that he reached out to colleagues to document other cases of eye syphilis around the country, warning that they could represent “a true epidemic.” Scattered reports of rising ocular syphilis have also occurred in France, Canada, and other countries.
The simplest explanation for the jump in eye-related cases could just be that syphilis of any sort has been on the rise in the U.S. for decades, says Amy Nham, an officer with the Epidemic Intelligence Service at the CDC who investigated the Chicago cases. Sexually transmitted infections of all kinds are increasing worldwide, thanks to a long-standing lack of access to testing and treatment, increasing drug use, and falling condom use.
In the U.S., syphilis is gaining ground with particular speed. More than 200,000 Americans were infected with syphilis in 2022, which experts believe is likely an underestimation due to lack of screening during the coronavirus pandemic. That’s almostdouble 80 percent more the number of cases than in 2018, and the highest number of documented cases since 1950. Experts aren’t quite sure why. The disease has always been a wily foe, combining the sneakiest qualities of several other STIs: chlamydia’s immune-evading powers, herpes’s ability to lie dormant for years, and gonorrhea’s trick of traveling through the bloodstream to faraway organs. Christina Marra, a neurosyphilis expert at the University of Washington Medical School, told me that syphilis also seems to be highly stigmatized even compared with other STIs like HIV, which could lead patients to avoid screening. In studies, Marra spoke with hundreds of men who had both HIV and syphilis. “They tell their mom about their HIV but they don’t tell their mom about their syphilis,” she said.
The idea that as infections continue to increase, so do the number of rare or extreme cases, including stand-alone eye syphilis, is the most accepted explanation among scientists. But several experts are concerned that a different,more unique situation is unfolding. Some of the recent eye-syphilis cases might suggest a new eye-loving strain of the disease. That would explain the fact that all the cases in the Michigan cluster occurred at roughly the same time within a small geographic area, and stemmed from a single partner. “That is very strong epidemiological evidence that there was something unique about the syphilis strain in this case,” William Nettleton, a family-medicine doctor and public-health researcher at Western Michigan University who documented the cluster, told me.
But in Chicago, the infections were documented over eight months, and occurred in hospitals all across the city. And past investigations have not supported the hypothesis of eye-loving strains, although they have found evidence for strains that are more likely to cause neurological symptoms. (Genetic sequencing is not part of standard clinical protocol, so no one attempted to sequence the strain types in the Chicago cases. A larger CDC study to identify any strains that may be associated with the eyes is ongoing.) Where symptoms show up in the body might be also influenced by a person’s individual immune system and risk factors, Leone said.
Nham and other experts are less concerned with any possible new syphilis strains, and more worried about the fact that the disease is rising in new populations. In the past, men who have sex with men, transgender women, and people with HIV were at highest risk. But syphilis is now rising in women heterosexual populations and heterosexual menpeople without HIV as well. Most of the cases in Chicago were among heterosexual people assigned male at birth without HIV. The Michigan cluster consisted of five HIV-negative women and one HIV-negative man. The man who went blind in North Carolina was heterosexual and HIV-negative. Of particular concern is the sharp rise in pregnant women, who can pass syphilis through the placenta, resulting in stillborn babies or ones who grow up with blindness, deafness, or bone damage.
Today’s apparent increase in neurological and ocular symptoms is a throwback to a time before penicillin, when about one-third of syphilis sufferers experienced neurological symptoms. In the 16th-century epic poem from which syphilis gets its name, the poet describes an unfortunate youth who, “his eyes, so beautiful, the clear mirrors of the day are devoured by a fearsome ulcer!” The Dutch painter Gerard de Lairesse and the Portuguese writer Camilo Castelo Branco are believed to have lost their vision from syphilis. Even Friedrich Nietzsche might have gone near-blind from the disease.
These unusual manifestations of syphilis are so antiquated that many doctors working today weren’t trained to recognize them in medical school. In fact, “there’s an entire generation of clinicians, including myself, who never saw syphilis in medical training because, in 1999 and 2000 when I was training, there was almost no syphilis in the U.S.,” says Ina Park, a sexual-health researcher at UC San Francisco and the author of the book Strange Bedfellows: Adventures in the Science, History, and Surprising Secrets of STDs.
But even if doctors were better trained to spot unusual symptoms, the communities most at risk—many of which lack access to testing centers, education, and treatment—might not benefit from that knowledge. The man who came to Leone in 2015 delayed going to the ER in the first place because he had no health insurance. If he had been able to see Leone two weeks earlier, he would likely still have his sight. During the pandemic, many STI clinics closed or switched over to virtual care; last year, Congress proposed a $400 million cut from the national STI-intervention workforce. And in the past year, doctors have faced an acute national shortage of Bicillin L-A, an injectable form of penicillin that is the most effective antibiotic for treating syphilis and the only one recommended for pregnant women.
To the uninitiated, a sudden outbreak of eye syphilis sounds like the plot of a horror movie. But to Leone, the cases in Chicago felt like déjà vu. “I’m going to be really honest, it didn’t surprise me at all,” he told me. We’ve known the cure for syphilis since 1943. The true horror is that the U.S. has allowed this ancient scourge to gain a foothold once again.
