Mpox still circulating in low numbers among MSM

Low-level transmission of mpox is still occurring, primarily among gay and bisexual men who have sex with men (MSM), according to findings from a recently published study led by researchers at the University of California, Los Angeles.

The ongoing transmission reinforces the need for healthcare professionals to promote mpox vaccination, particularly among high-risk individuals (MMWR Morb Mortal Wkly Rep 2024;73[22]:507-513).

The study focused on prospective surveillance of patients ages 3 months and older who had an mpox-compatible rash, and was conducted at 13 emergency departments from June through December 2023. Lesions were tested for mpox, and information such as demographics and illness characteristics were collected by electronic health records and questionnaires.

A total of 196 people were enrolled, 6.6% of whom were gay and bisexual MSM; 46.4% were non-Hispanic white, 23.5% non-Hispanic Black and 38.8% Hispanic. Unstable housing was reported by 10.7% of the study participants.

Among the individuals, prevalence of mpox was 1.5%. All people who had a confirmed mpox diagnosis identified as MSM, were HIV-negative, had not been vaccinated against mpox and reported having engaged in sex with at least one partner they had met via smartphone dating apps. No cases were found in women, children or the unhoused.

“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 David Talan, MD, a professor of emergency medicine/infectious diseases and emergency medicine at the David Geffen School of Medicine at UCLA.

This enabled them to investigate whether infection was occurring in groups outside of MSM who might have been missed for testing because of their demographics, he explained.

“Because the surveillance was rash-based, we were able to feel pretty secure that we looked to see where mpox was in any type of person, as opposed to the suspicion of the diagnosis being limited by what we already know about the overwhelming epidemiology of this association with unprotected sex and MSMs,” Dr. Talan told Infectious Disease Special Edition.

Overall, Dr. Talan stressed that the study findings reinforce the importance of receiving two appropriately spaced doses of the Jynneos vaccine, particularly among those who are at high risk for mpox. This is particularly true, he said, as public health officials keep an eye on a new mpox clade (clade I), which has emerged in the Democratic Republic of the Congo and which may be both more transmissible and virulent than the clade that was responsible for the 2022 global outbreak (clade II).

“People living their lives and having relationships need to be aware of this,” he said. “People who are engaged in at-risk behavior need to think about changing that behavior, but there is also a safe and effective vaccine; those individuals in particular should be encouraged to get vaccinated.

“There is a big potential to protect the population by getting more people aware that they are at risk and that they can protect themselves via vaccination,” Dr. Talan added.

By Ethan Covey