Key Factor in Monkeypox Spread: One-Time Sexual Partners

Marcia Frellick

August 29, 2022

New modeling data by the Centers for Disease Control and Prevention (CDC) show that reducing the number of one-time partners in sex between men may be a key factor in slowing the spread of monkeypox.

Ian Spicknall, PhD, with the CDC Monkeypox Emergency Response Team, led the modeling study published Friday in the Morbidity and Mortality Weekly Report (MMWR ).

Researchers found that men who have sex with men (MSM) who had more than one partner in the past 3 weeks had 1.8 to 6.9 times the risk for monkeypox infection compared with those who had one partner in the past 3 weeks, depending on the transmission scenario.

The percentage of such partnerships is small — one-time partnerships represent less than 3% of daily partnerships and 16% of sex between men each day, the authors note. But one-time partnerships accounted for 50% of all monkeypox transmissions.

The model indicates that reducing such partnerships has a large effect. The authors write, "a 40% decrease in one-time partnerships yielded a 20%-31% reduction in the percentage of MSM infected and a delay in the spread of the outbreak."

"If decreasing one-time partnerships were combined with additional mitigation measures such as vaccination or shorter time from symptom onset to testing and treatment, this effect would be higher," the authors write.

Peter Chin-Hong, MD, an infectious disease specialist with University of California, San Francisco, told Medscape Medical News, "I think [the study] corroborates what we suspected biologically based on how this outbreak is going. It gives us good insight into how we can tailor messages."

"The value of the study is to put a number on it," he said, which can help public health officials and people in the community know where changes make the most impact. Chin-Hong was not involved in the study.

Since late May, the US has recorded nearly 17,000 monkeypox cases. The outbreak is largely being transmitted among gay and bisexual men.

Reduction in Risky Behaviors

Chin-Hong added that there is evidence that partner behavior is already changing among MSM and that people in the community are reducing the number of sexual partners and reducing activity on dating apps such as Grindr.

Another CDC study published on Friday in the MMWR shows the extent of those reductions.

The authors, led by Kevin P. Delaney, PhD, also with the CDC Monkeypox Emergency Response Team, report that in a recent survey of MSM taken August 5 to 15 about half reported reducing their number of sex partners, one-time sexual encounters, and use of dating apps because of the monkeypox outbreak.

Vaccine Supply Remains Limited

Current vaccine supply is limited, so measures that might slow the spread, such as fewer one-time partnerships, could be critical for lowering the cumulative infection rate, the authors note.

The Delaney et al survey study, which used data from the American Men's Internet Survey (AMIS), highlighted inequities in uptake of the monkeypox vaccine. AMIS is an annual, cross‐sectional, online behavioral survey of cisgender men in the US who report sex with another man in the last year.

A total of 151 respondents (18.6%) reported having at least one dose of the vaccine.

Vaccine uptake was highest among Hispanic men (27.1%) and lowest among Black men (11.5%). Uptake for white men was 17.7%. And uptake among men of another race and ethnicity was 24.2%.

Wafaa El-Sadr, MD, MPH, an infectious disease specialist at Columbia University in New York City and leader of the Pandemic Response Institute at the Mailman School of Public Health, told Medscape Medical News, "This is a disparity we need to address rapidly."

She said both CDC papers help focus the message in slowing monkeypox spread.

Impact Will Come From Combined Interventions

El-Sadr, who was not involved in the study, noted that reducing one-time partnerships is just one part of controlling the disease.

"The biggest impact will come by being strategic and nimble and being able to use the combined interventions," she said.

She said it’s important in communication with communities at risk to make the distinction that one-time partnerships described in these studies are when a man has sex with a man once and may or may not ever have sex with that same man again. It's not to be confused with, for instance, men having a sexual partnership with only one man.

El-Sadr noted that monkeypox numbers are coming down in areas including New York, and that is a hopeful sign.

"There's the beginning of evidence of a plateau and a decrease in daily cases, which is very encouraging," she said. She added, however, that for every case known about there are many cases not reported.

Spicknall, Delaney, Chin-Hong, and El-Sadr have disclosed no relevant financial relationships.

Marcia Frellick is a freelance journalist based in Chicago. She has previously written for the Chicago Tribune, Science News, and, and was an editor at the Chicago Sun-Times, the Cincinnati Enquirer, and the St. Cloud (Minnesota) Times. Follow her on Twitter at @mfrellick.

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