In a disease cluster last year, one infected but asymptomatic man spread a rare form of syphilis that affects the eyes to five Michigan women, a new report finds.
Since ocular syphilis remains very rare, researchers believe the strain of T. pallidum -- the syphilis bacterium -- that the man carried might have raised the risk for eye complications in his sex partners.
The man and the five middle-aged white women he infected eventually all received penicillin treatment and were cured. So the researchers say it's possible that the strain "ceased to circulate after these patients and their common partner were treated," although no one can know that for sure.
The study was led by Dr. William Nettleton of the Kalamazoo County Health and Community Services Department in Kalamazoo, Mich. His team reported the findings in the Nov. 24 issue of Morbidity and Mortality Weekly Report, a journal of the U.S. Centers for Disease Control and Prevention.
Syphilis is making an unwelcome comeback among sexually active Americans everywhere. According to Nettleton's group, in Michigan cases-per-100,000-people rose from 3.8 in 2016 to 9.7 by 2022.
Most of the rise in cases was concentrated in southwest Michigan (the area around Kalamazoo).
Syphilis is an insidious infection, because in many cases it does not cause symptoms although the bacterium can still be transmitted to others.
Over time, syphilis can trigger serious neurological symptoms, including permanent damage to vision.
In the 2022 outbreak, five white Michigan women ranging from 40 to 60 years of age ended up in hospitals with ocular syphilis. According to the new report:
In March, patient "A"reported "blurred vision [and] fear of blindness."
In April, patient "B"was admitted to hospital with neurosyphilis, after reporting headache, hearing loss and "worsening blurry vision and double vision."
In May, patient "C"tested positive for syphilis and experienced a "a full body rash and peeling skin on her hands,"along with "spots drifting through her field of vision."
In June, patient "D"received a diagnosis of ocular syphilis from her ophthalmologist. She also experienced genital sores and a rash on her hands and abdomen.
In May, patient "E"complained of vision issues and by July was admitted to hospital with ocular syphilis and neurosyphilis.
All of the women had had sexual relations with the same man, often first connecting with him online. When state health workers tracked him down in May 2022, he showed no symptoms of syphilis but "reported having multiple female sex partners during the previous 12 months."
His tests for syphilis came back positive and -- like the five women already identified in the outbreak -- the man received a curative penicillin injection which resolved the infection.
While other outbreaks of ocular syphilis have been recorded, the Michigan outbreak "is the first documented "¦ among cases attributable to heterosexual transmission,"Nettleton's group noted in its report.
What's also concerning is that complications involving the eyes typically occur in more advanced cases of syphilis, but in the new cluster "all patients had early-stage disease,"the researchers said.
Also, unlike many clusters seen before, none of these patients "reported injection drugs use or transactional sex,"and all were HIV-negative.
Although a majority of syphilis cases in Michigan last year occurred in men, researchers noted that the proportion of syphilis cases occurring among women" has increased from 9% in 2016 to 23% in 2022."
Nettleton and colleagues are advising doctors to be on the alert for cases of syphilis, because "prompt diagnosis and treatment of syphilis can prevent systemic complications, including permanent visual or hearing loss."
More information
Find out more about syphilis at the CDC.
SOURCE: Morbidity and Mortality Weekly Report, Nov. 24, 2023
