A surge of mpox in the Democratic Republic of Congo has raised concerns of another global outbreak with more deaths than the one ignited last year, prompting scientists to worry the world will again fail to recognize warnings from Africa.
For the first time, scientists have identified sexual transmission of a version of the mpox virus that is linked to more fatalities in a region where mpox is endemic and more typically transmitted through contact with infected animals.
The Centers for Disease Control and Prevention on Wednesday warned people who have traveled to Congo to be on the lookout for rashes caused by the virus and issued a similar alert to health providers on Thursday. The World Health Organization released a report in November detailing Congo's worst surge on record, with nearly 13,000 suspected cases and 581 suspected deaths this year.
While there's no evidence of another global outbreak starting, health authorities are especially attuned to a virus that was declared an international and U.S. health emergency last year.
The WHO warned that the situation in Congo, if not controlled, poses a significant risk of international outbreaks "with potentially more severe consequences than the one which has been affecting the world since 2022."
The unfolding situation underscores long-standing tensions about how mpox is treated in African countries where it's endemic, renewing questions about health equity: Has the world failed to learn that infectious-disease threats in poor countries pose global threats? Why isn't the vaccine that helped quell the mpox outbreak in the West available in Africa? And would homophobia and stigma inhibit efforts to contain sexual transmission of the virus in Congo?
Mpox circulated broadly outside of Africa for the first time last year, infecting more than 92,000 worldwide, mostly through male-to-male sexual contact. Authorities traced the international spread to festivals and other large events where men had sex with other men.
Experts were relieved that cases outside of Africa were driven by a group of viruses, known as clade 2b, that caused less severe disease. The global death toll from confirmed mpox cases is 167 since 2022, according to the WHO. People with untreated HIV who contract mpox face higher risk of death.
"The story of mpox didn't end last year," said Jason Kindrachuk, an associate professor of medical microbiology and infectious diseases at the University of Manitoba's Max Rady College of Medicine who is studying Congo's outbreak. "This has been a five-decades-long struggle for people that inhabit endemic regions of the world."
Now authorities have confirmed sexual spread of clade 1 in Congo in at least two dozen cases; clade 1 has a higher fatality rate than the version that spread internationally last year. A cluster of several cases in people who had sex with an mpox patient has caught attention, as has an unconnected case involving a man who has sex with other men and an outbreak that includes 20 sex workers in an eastern province of Congo that had never reported mpox before.
The discoveries are concerning because sex has proved to be a far more efficient way for the virus to spread than other forms of skin-to-skin contact, animal bites and scratches, or consuming contaminated bushmeat. Nonsexual spread had accounted for most transmissions in parts of Africa where the virus has circulated for decades.
It's unclear to what extent sex is driving the broader surge of the virus in Congo, where mpox cases this year are more than double the previous high of 6,216 cases reported in 2020. Every 2 out of 3 tests are coming back positive, a high rate that suggests the virus is more widespread than the official tally, according to the WHO. Infections have spread throughout the country in places that had not previously reported the virus, including urban areas such as the capital, Kinshasa, and provinces that border other countries.
"Something new might be happening," said Rosamund Lewis, the WHO's technical lead on mpox, in an interview from Kinshasa. "If these newly described outbreaks of sexually transmitted infection are not controlled at the source, the virus may circulate more widely in the same manner as clade 2 is circulating."
So far, there's no evidence sexual transmission of the clade 1 outbreak has spilled outside of Congo. But Lewis cautioned that bordering countries are at risk because of the high mobility of sex workers who are contracting the virus.
In its alert, the CDC said none of the 150 U.S. mpox cases sampled this year for deeper testing belonged to clade 1.
The CDC declined repeated requests for an interview but issued a statement saying that "the anticipated risk to the United States is low" and would be primarily among those who traveled to Congo. Those who did and develop new or unexplained rashes should immediately seek medical care and tell their doctor they were recently in Congo, officials said.
Disease detectives traced a cluster of sexually transmitted clade 1 mpox cases in Congo to a man who probably contracted the virus in Europe after having sex with someone who frequently visits Congo. The man then traveled to Congo, and three of his sexual partners there, including one woman, later tested positive for mpox, according to research published last week in the CDC's Emerging Infectious Diseases journal. He had also visited gay sex clubs, and some members of sex clubs in Congo also frequent clubs elsewhere in central Africa and in Europe, raising concerns of international spread.
But there's no evidence that happened, and this particular chain of transmission appears to have been broken, though health officials caution there may be other cases of sexual spread going unnoticed.
The international health community had taken little notice of a 2019 report documenting unusual sexual transmission of mpox in Nigeria, and three years later was surprised by the rapid global sexual spread of the once-rare virus.
Researchers say the world has an opportunity to support vaccination in central Africa to prevent another global outbreak that could be deadlier. The fatality rate in Congo from mpox overall has been 5 percent this year, though death rates are usually lower in countries with better access to health care.
Some experts say it's galling that the Jynneos vaccine for mpox is now widely available in the United States - where cases have dwindled to several a week - but not in Congo or other nations where the virus is endemic. The Biden administration had to scramble last year to increase vaccine supply.
"We are just simply witnessing a double standard," said Gregg Gonsalves, an associate professor of epidemiology at the Yale School of Public Health and member of the International Mpox Research Consortium.
Bavarian Nordic, which manufactures the Jynneos vaccine, said it has not been approached by African nations seeking vaccines in the last two years and has encountered regulatory hurdles in donating it.
"Bavarian Nordic is willing to support the current situation in the DRC and monitoring it closely," chief executive Paul Chaplin said in a statement. "JYNNEOS is not approved in the DRC, or any other country in Africa, so the issue of liability/indemnification has to be resolved whether doses are sold or donated."
Anne Rimoin, an epidemiologist who has studied mpox in Congo for two decades, said even if the two-dose vaccine were approved, distribution would be "exponentially complicated" in a poorly resourced country with competing public health priorities and logistical challenges in bringing shots to rural areas. She also said people who belong to highly stigmatized groups at greater risk of contracting the virus can be harder to reach and may not feel comfortable accessing medical care.
"It's not just as simple as handing over vaccine and saying have at it," said Rimoin, a professor of epidemiology at the UCLA Fielding School of Public Health.
The confirmation of male-to-male sexual spread in Congo also exacerbates stigma concerns.
Health officials had tread carefully last year when acknowledging mpox cases outside of endemic countries were overwhelmingly in gay and bisexual men. That can be especially difficult in parts of Africa where homosexuality is taboo or even criminalized. Same-sex relations are not illegal in Congo, but the prevalence of underground sex clubs illustrates how homosexuality is frowned upon. Experts worry people may not seek treatment when they have genital lesions.
"It becomes almost a scarlet letter," said Boghuma Kabisen Titanji, a physician who has treated mpox patients in Atlanta and trained in Cameroon, where mpox is endemic. "It's very difficult to provide care or efforts for prevention when you have to thread the needle from protecting communities that can be vulnerable targets and getting the education and testing resources that are needed by these communities."
Experts also warned against drawing simplistic comparisons between Africa and the West when it comes to bigotry. Homophobia also complicated the mpox response in the United States, where some people were hesitant to disclose sexual history to get vaccinated or worried about developing a telltale mark on their arm from a shot associated with gay men.
While the worst days of the mpox outbreak in the United States are over, peaking at nearly 450 daily infections in August 2022, the country still sees sporadic cases, including 28 in November.
"We did not stamp it out," said Gonsalves, of Yale. "Homophobia and stigma is still going to present a barrier in the U.S. for dealing with this as a low-level endemic situation."