Five Cases of Ocular Syphilis Traced to One Partner in Southwest Michigan, 2022

Untreated syphilis can spread beyond the genitals and skin to the eye (ocular syphilis), the inner ear (otosyphilis) or the central nervous system (neurosyphilis). These complications are rare. In 2022, Michigan health officials found five women with ocular syphilis who had all had sex with the same man, the first documented cluster of its kind linked to heterosexual transmission. It suggests that an unidentified strain of the syphilis bacterium, Treponema pallidum, may have carried a higher risk of these complications.

How it was found

In Michigan every reactive syphilis test is reported to the state's disease surveillance system; the state health department (MDHHS) runs case investigation and contact tracing, while local health departments and hospitals handle treatment. On April 21, 2022, a public health physician at the Kalamazoo County Health and Community Services Department (KCHCSD) told the state that two hospitalised women from the same area had been diagnosed with ocular syphilis within 5 weeks. They turned out to share a male sex partner.

Investigation and response timeline, southwest Michigan, 2022. CDC.

The five women

All five lived in different southwest Michigan counties, were aged 40–60 (mean 49.0), identified as White, were HIV-negative, and reported no drug use or transactional sex. All had early-stage syphilis, were hospitalised and treated with intravenous penicillin.

• Patient A, referred in March by an eye specialist, had blurred vision and genital sores that had not improved on treatment for presumed herpes; she was diagnosed with primary and ocular syphilis. She had met her recent partner online.
• Patient B, admitted in April with neurosyphilis after 4 weeks of headache, mild hearing loss and worsening blurred and double vision treated elsewhere with other medicines, named the same partner, also met online.
• Patient C, reported in May, had a full-body rash, peeling palms, floaters and sensitivity to light; she too named the same partner, met online.
• Patient D, diagnosed in June after worsening vision, had had genital sores and a rash treated with steroids; she named the same man as a partner in January 2022.
• Patient E, seen in May for floaters, flashing lights and worsening sight after cataract surgery, had a positive screening test but no follow-up test, since not every positive screen means an infection that can be passed on; she was admitted in July with neurosyphilis and ocular syphilis. She had been with the same man during February–April 2022.

Treatment was offered to every sex partner of the women who could be reached; the other partners contacted tested negative or reported negative results.

The common partner

State disease intervention specialists reached the man several times by phone and text in March–May 2022. He gave little information, said he had travelled out of state and missed an April appointment. Reviewing his medical records in May, a local public health physician found he had gone to an emergency department in January with ulcers on the penis and anus, had been treated for presumed herpes, and had not been tested for syphilis. He then kept an appointment at the county clinic in May: he had no signs of syphilis and no vision or hearing problems, but tests confirmed early latent syphilis, and he was treated with one injection of penicillin. He reported several female partners in the past year but would not name them. Patients A and B both recalled a sore on his penis in January.

No further transmission was found after he was treated. Molecular typing of the strain was not possible: the few specimens held too little genetic material.

How unusual it was

• A 2019 study of 41,187 syphilis cases in 16 jurisdictions found neurosyphilis and ocular syphilis in 1.1% each and otosyphilis in 0.4%.
• Complications are usually seen in late-stage disease, in people 65 and older and in people who inject drugs. These women had early disease, were 40–60 and reported no injection drug use.
• Among 43 other Michigan ocular syphilis patients in the same period, 19% had HIV, 2% reported injection drug use and 7% transactional sex.
• Earlier clusters were different: in Seattle in 2015, four men who have sex with men, three with HIV and two of them partners; and among 139 suspected ocular syphilis cases with partner data from four jurisdictions in 2014–2015, no partner had ocular syphilis.

Syphilis is rising in Michigan: the rate of primary and secondary syphilis went from 3.8 per 100,000 in 2016 to 9.7 in 2022, increasingly in the southwest, and women's share of cases rose from 9% to 23%. The authors note that neither this nor any difference in how cases are found explains five women sharing one partner, and no shared susceptibility among them was identified. A particular strain that stopped circulating once the women and their common partner were treated is possible, but without typing it cannot be confirmed.

The response

In late April the state and county sent providers an infographic on the signs of ocular syphilis, otosyphilis and neurosyphilis; it prompted a physician to alert a sixth patient, a man not linked to the cluster, who then sought care. In early May the county issued a health advisory through the Michigan Health Alert Network, and in June a statewide webinar on diagnosis and treatment featured the cluster.

Lessons

• Clinicians should keep syphilis in mind and take a thorough sexual history, in every setting.
• People at risk of syphilis, and people with it, should be checked for neurological, eye and hearing symptoms; anyone with syphilis and eye complaints should see an eye specialist at once, and any cranial nerve problem should prompt a spinal fluid test, before treatment if possible.
• Prompt diagnosis and treatment prevent permanent loss of sight or hearing, and linking surveillance with partner investigation and treatment referral can stop transmission, as it did here across county lines. CDC's 2021 STI treatment guidelines cover treatment.

Sources

• Nettleton WD, Kent JB, Lightheart K, Diesel JC. "A Cluster of Ocular Syphilis Cases with a Common Sex Partner — Southwest Michigan, 2022," MMWR. https://www.cdc.gov/mmwr/volumes/72/wr/mm7247a1.htm