Study finds mpox continues to circulate at low numbers among gay and bisexual men who have sex with men

While mpox cases have sharply declined since the 2022 global outbreak, they continue to occur in the U.S. among gay and bisexual men who have sex with men (GBMSM), according to a UCLA-led study from EMERGEncy ID NET, a multi-site surveillance network.

Though no cases were found in women, children or the unhoused, vigilance and vaccination remain important, the researchers write.

The findings will be published June 6 in Morbidity and Mortality Weekly Report.

Mpox, formerly known as monkeypox, is an infection endemic in Africa that is transmitted by skin-to-skin contact. The infection causes fever and painful skin blisters, and is usually self-resolving, but rarely causes death in immunocompromised individuals. In 2022, there was a global outbreak that primarily affected GBMSM, with more than 30,000 cases reported in the U.S.

Cases sharply declined by late 2022 due to public education efforts and vaccination. However, concern for mpox's reemergence persists because of low vaccination coverage among GBMSM and incomplete knowledge of risk among other groups, including women, children and the unhoused. There have been recent local outbreaks in major metropolitan areas, including Chicago and Los Angeles.

The new study was conducted from June through December 2023. Of 196 enrolled persons, about 45% were female, 20% were children and 10% had unstable housing and over half identified as non-white. Mpox was diagnosed in three (1.5%) individuals, each of whom identified as GBMSM and reported being HIV-negative, not being vaccinated against mpox, and having engaged in sex with one or more partners met on smartphone dating applications.

"This surveillance effort was unique in that it was based on testing all patients with an mpox-compatible rash regardless of presumed epidemiological risk," said Dr. David Talan, professor of emergency medicine/infectious diseases at the David Geffen School of Medicine at UCLA and the study's co-lead.

"This allowed us to investigate whether infection occurred in non-GBMSM individuals, groups who previously may not have been suspected and tested for mpox."

Public health officials are currently closely monitoring a new mpox strain in the Democratic Republic of the Congo because it appears to be more transmissible and virulent, said study co-lead Dr. Carl Berdahl, assistant professor of medicine and emergency medicine at Cedars-Sinai Medical Center in Los Angeles.

"Clinicians should remain vigilant for mpox infections, particularly in GBMSM, and educate patients on risk reduction, including the importance of vaccination," Berdahl said.