Monkeypox, Sex and Transmission: What We Know, What We Don't

Monkeypox continues to spread around the world with at least 92 confirmed cases and 28 suspected cases being reported as of May 21 from countries where the virus does not usually spread.

Amid news of the outbreak, the Joint United Nations Programme on HIV/AIDS (UNAIDS) warned against reinforcing "homophobic and racist stereotypes" since most—but not all—cases so far have occurred in men who have sex with men (MSM), according to the World Health Organization (WHO).

David Heymann, a WHO infectious disease specialist, told Reuters over the weekend that monkeypox seems to have gotten into the population "as a sexual form."

People in bed
A stock photo depicts two people lying in bed after sex. Monkeypox, a viral disease, may spread through sexual contact. dima_sidelnikov/Getty

However, scientists are still working to understand why the disease is spreading so uncharacteristically and whether the virus has changed somehow.

Several experts have spoken to Newsweek to discuss the sexual spread of the ongoing monkeypox outbreak. Here's what we know and what we don't.

How monkeypox spreads

Monkeypox is caused by a virus of the same name that can infect people by entering the body through broken skin, the respiratory tract, or mucous membranes like the eyes, nose, or mouth, according to the U.S. Centers for Disease Control and Prevention (CDC). People can also catch it through direct contact with bodily fluids or lesion material.

"Human-to-human monkeypox transmission is believed to be quite inefficient, thus it requires close contact," Roger Paredes, member of the World Health Organization (WHO HIV Drug Resistance Strategy Steering Committee and of the U.S. International Antiviral Society, told Newsweek. "The main routes of transmission between humans are airborne, through contact with skin or mucosal lesions, body fluids, but also with bedding. The secondary attack rate is usually 3 percent, but in close contacts can increase to 50 percent."

It is easy to imagine how sex would make it easier for monkeypox to spread via the routes described above.

So is monkeypox an STD?

This is a nuanced question. While monkeypox does appear to be somehow related to sex in some cases, this does not necessarily mean it has become a sexually transmitted disease, said Jason Mercer, professor of virus cell biology at the University of Birmingham in the U.K. He told Newsweek: "Monkeypox does not usually spread very well from person-to-person as it requires extended contact with respiratory droplets or lesions.

"That said, extended direct contact with monkeypox lesions, i.e. during sex, could facilitate human-to-human transmission. So strictly speaking I would not classify Monkeypox as a sexually transmitted disease, but as a contact transmissible disease."

That said, some diseases which are generally classified as STDs, such as HIV and the Herpes Simplex Virus, are not limited to sexual contact. "HIV can be spread through blood transfusions, or from mother to child during breast-feeding," Mercer said.

"I think this definition of an STD is a misnomer. While STDs, for example HIV and HPV, are most-often transmitted through sexual contact, I don't know of any diseases that are exclusively transmitted through sexual contact."

What about the monkeypox cases in MSM?

As mentioned, cases in the current outbreak have mainly been identified in MSM according to the WHO.

Matthew Kavanagh, deputy executive director of UNAIDS, has voiced concern about how this has been reported and stressed in a statement published on Sunday: "Stigma and blame undermine trust and capacity to respond effectively during outbreaks like this one."

UNAIDS said that despite the MSM cases the risk of monkeypox is not limited to this group and could affect anyone.

The point was echoed by Mike Skinner, reader in virology at the Department of Infectious Disease at Imperial College London. He told Newsweek that monkeypox may also be spread in heterosexual communities and cautioned against focussing on sexuality.

"If a young, sexually active heterosexual is infected, and his contacts have same proclivity, then it could spread in the way we're seeing at moment, albeit within those of different orientation," said Skinner. "So we shouldn't be focusing on sexuality but on numbers of close/intimate contacts, not one-on-one but in the extended contact network.

"I think we're seeing that it [is] more likely that sex has simply facilitated transmission via a respiratory/mucous/lesion contact route, amplified by penetration of extensive networks with close or intimate contact."

For now, the WHO has said the situation is evolving and said in a May 21 statement: "Someone who has direct contact with an infected person, including sexual contact can get monkeypox. Steps for self-protection include avoiding skin to skin or face to face contact with anyone who has symptoms, practicing safer sex, keeping hands clean with water and soap or alcohol-based hand rub, and maintaining respiratory etiquette."

Correction, 5/23/22, 11:24 a.m. ET: This article has been updated to correct the name of professor Jason Mercer, whose quotes were previously incorrectly attributed.