“Explosive” Mpox Outbreak Overwhelms Health System in Sierra Leone

Surprise! It’s still not a gay disease!

Science magazine’s June 2 issue reported that the “rapid transmission” of mpox in the small West African nation of Sierra Leone appears to be completely out of control. (1)

Contributing correspondent Kai Kupferschmidt did his best to create a gay “Patient Zero” for mpox—like the fictional first AIDS patient in Randy Shilts’s And The Band Played On—by asserting that one man from Sierra Leone’s capitol Freeport traveled to a small town named Lungi, where he had sex with a sex worker. He developed a rash, became “desperately ill,” and returned to Freeport, where he was diagnosed with mpox, according to Njala University epidemiologist Jia Kangbai. (1)

“His was the first reported case in what soon became a massive mpox outbreak,” Kupferschmidt asserted. Sierra Leone has a population of about nine million people; it currently has “three-quarters of all new mpox cases in Africa,” more than 3000 at last count. (1)

Like the often-anthropomorphized HIV—characterized as “wily” and “devious” and even sillier descriptors for a tiny ball of RNA that hasn’t actually been shown to cause Kaposi’s sarcoma or PCP or AIDS or anything else—the mpox virus is developing a whole range of personalities in the medical literature.

Mpox virus has two “clades” or variants: clade Ib has been associated with recent outbreaks in the Democratic Republic of the Congo (DRC) and neighboring Burundi, but only among men who have sex with men, according to Kupferschmidt.

In Sierra Leone, the second variant—clade IIb—is causing “many serious cases, including people who have lesions all over their bodies.” Additionally, it’s “shaking up thinking about the two known varieties of mpox,” according to Yap Boum, deputy lead of a team set up by the World Health Organization and the Africa CDC. (1)

How so?

“The variant [clade IIb] is behaving very differently in Sierra Leone,” Kupferschmidt reported. “Its explosive spread, combined with the fact that cases seem evenly split between men and women, initially led some scientists to believe the virus might have undergone changes that make it more transmissible without sexual contact. ‘The spread of Mpox in Sierra Leone is unlike anything we have ever seen,’ Kristian Andersen, an evolutionary biologist at Scripps Research, wrote on Bluesky on 22 May. ‘This could be the next one.’ ” (1)

If that last comment left you asking, “Wait, what?” like it did me, it’s because Andersen’s post on Bluesky wasn’t reported exactly as it appeared on the app. Here’s what Andersen actually posted:

Why does Andersen seem so apprehensive? Let’s review: Originally, it was determined that clade Ib mpox was a sexually transmitted disease only among men having sex with men, and no other demographic, in the DRC and Burundi.

Now, however, that clade Ib variant is causing an outbreak among men and women equally in the DRC and Burundi. While researchers believe these cases are also sexually transmitted—like the cases in men who have sex with men—many patients of each gender have “severe cases” of mpox with lesions all over their bodies.

Simultaneously, the second mpox virus variant—clade IIb—is causing the same serious disease with widespread lesions, equally distributed between men and women, in a third country, Sierra Leone.

Here’s a limited timeline:

Outbreak #1: Clade Ib mpox virus caused an outbreak in men having sex with men in the DRC and its neighbor Burundi during 2022.

Outbreak #2: Clade IIb mpox is currently causing an outbreak in Sierra Leone that affects men and women equally, causing them to develop “severe disease” with lesions all over their bodies.

Outbreak #3: Back in the DRC and Burundi where this all started, the original clade Ib mpox virus is now also causing severe disease, equally distributed in men and women, many of whom have lesions all over their bodies.

“We are still a bit puzzled by what is going on,” Boum commented. “The situation [in Sierra Leone], while it is due to clade IIb, looks like a clade Ib in terms of transmission mode but also clinical features.” He added that a team of ten more epidemiologists will be sent to investigate. (1)

And while most of these investigators are certain that mpox is a sexually transmitted disease of men who have sex with men, they keep finding heterosexual patients who are severely ill and develop mpox lesions all over their bodies. Understandably, the researchers are perplexed.

Perhaps these outbreaks would be less confusing to investigators if they didn’t immediately, upon encountering a gay man with a rare-ish disease, assume that it’s a sexually transmitted condition that has a wily virus—able to distinguish between men, women, and men who have sex with men—to blame.

And meanwhile, who’s caring for the seriously ill patients in these African countries where the limited health systems have already been overwhelmed? How are they being treated? With what? Could a little bit of this brain trust be put to work figuring out a treatment for this painful, disfiguring disease, even if it’s only symptomatic?

BIBLIOGRAPHY
1. Kai Kupferschmidt. “Explosive mpox outbreak in Sierra Leone overwhelms health systems.” Science News, June 2, 2025. doi: 10.1126/science.zpireve