Researchers in France and Spain diagnosed dermatitis in a large number of men who had sex with other men. Dermatitis is a skin disease that usually affects livestock, but contact with infected animals was not known. One of the researchers told STAT that cases have also been confirmed in Germany.
In some ways, this outbreak is reminiscent of the emergence of mpox in networks of gay men and men who have sex with men in 2022. However, those who have diagnosed some of these dermatitis cases describe a disease with much milder symptoms.
This infection is caused by the bacterium Dermatodermatitis congolensis.
In an article published ahead of print in the Centers for Disease Control and Prevention’s Emerging Infectious Diseases journal, doctors reported small outbreaks in Barcelona and Lyon, with the latter group having some ties to Paris and several other French cities.
Vicente Descalso, lead author of the paper on the Spanish cluster, told STAT that after the paper was published on the journal’s website, a doctor in Berlin contacted him and informed him that there were cases in Berlin as well. Mr. Descalso is an internal medicine specialist working in the STI/HIV department at Drassanes Hospital Val d’Hebron in Barcelona.
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The main symptom of this disease is a rash. The authors of the paper on the French cluster reported that pimples and pustules mainly appeared on body parts exposed during sexual contact.
All cases diagnosed to date have been mild and have either resolved spontaneously or been successfully treated with antibiotics. This bacterium appears to be sensitive to multiple antibiotics.
Both study groups reported that most infected men reported going to a sauna before developing the rash. Descalzo cautioned that the possible role of saunas in infection is still only hypothetical, but the bacteria is known to spread more efficiently in humid environments.
“Humidity is a very important factor for the development of dermatitis congolensis,” Didier Pin, a veterinarian at VetAgro Sup, a veterinary university in Lyon, told STAT via email.
The Lyon group reported nine cases, one of which they said involved multiple sexual partners in a sauna in Paris. Genetic sequencing of bacterial samples from eight of the cases showed strong similarities.
“The combination of close genomic relatedness and common sexual exposure among the eight sequenced isolates suggests human-to-human transmission within sexual networks,” wrote the authors, who work at Lyon University Hospital.
The Barcelona team also reported nine cases, all of whom revealed they had visited a sexual setting in the week before symptoms appeared. Eight out of nine people participated in the sauna. Four of the men reported recent travel to other parts of Europe and sexual contact. None of the men reported contact with livestock.
Similar to the Lyon cluster, genetic sequencing of bacteria from the Barcelona cases showed that they were all closely related to each other, suggesting there was a single introduction of Dermatitis congolensis into this community, the authors said.
At the time of the interviews, neither group was comparing their sequences to sequences produced by the other group.
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Since the paper was submitted for publication, the Lyon team has confirmed more cases (25 in total) in Lyon, Paris, Bordeaux, Saint-Etienne and Annecy, said Matthew de Glayse, lead author of the paper and junior scientist at the hospital. One of the cases recently occurred in Türkiye. The other was in Italy, where they had a sexual relationship. I had no symptoms at that time.
DeGlaise said Lyon researchers suspect the two people may have been infected while traveling. But neither they nor the Barcelona researchers know whether men who are infected but don’t yet have lesions can transmit the dermatitis bacteria.
Although the Barcelona group has confirmed only one additional case, Descalso said that after posting about the paper on social media, he had heard from other doctors in the Barcelona area who said they had also seen one or two cases.
Both Descalzo and DeGlaise believe the condition is underdiagnosed. DeCalzo said he expects that given the mild nature of the symptoms, doctors will only need to prescribe antibiotics, which will likely end the infection more quickly in most cases.
Demetre Daskalakis, former director of the HIV prevention division at the U.S. Centers for Disease Control and Prevention, agreed that the more health care providers and researchers investigate, the more cases they are likely to confirm. However, it is still unclear how important this pathogen is to humans. “The question becomes, what does that mean in the real clinical world?” he said.
In animals, this bacterium causes pustules and lesions primarily in cattle, sheep, and horses. Depending on the species of animal and the part of the animal’s body affected, the disease may also be known as rain scald or rain rot, grease heel, or strawberry foot rot. Symptoms are mostly mild, but in some cases they can progress to more severe disease.
It is unclear whether this also applies to humans. But there are concerns about how the infection manifests when infected with uncontrolled HIV or another condition that compromises the immune system. None of the infected people in the Lyon and Barcelona clusters had weakened immune systems.
Daskalakis, who left the CDC last summer to protest the firing of then-director Susan Monarrez, expressed some concern about the outlook for these infections.
“It looks like pretty benign folliculitis,” Daskalakis said, referring to the common skin disease where hair follicles become inflamed and small pimples form.
“That’s a good thing, but we don’t know what will happen if you have people who are immunocompromised, and I think that’s probably the thing to be most concerned about,” said Daskalakis, now chief medical officer at the Cullen Lord Community Health Center in New York City. When he left the CDC, he was director of the National Center for Immunization and Respiratory Diseases.
Ping agreed that if the spread of the bacteria continues, this will be something to watch out for.
“Comorbidities can worsen dermatitis in animals, and I think it’s the same in humans, even though it’s much rarer,” Ping said in an email.
Daskalakis also worried that if the bacteria continued to spread within networks of men who have sex with men, it could become difficult to confirm mpox cases when patients with mpox seek diagnosis. But Descalzo said he doesn’t think that’s a problem for doctors trained to detect sexually transmitted diseases.
“Anyone who works in a sexually transmitted disease clinic would be familiar with what symptoms mpox causes, and for me, the cases (of dermatitis) that I personally saw in the clinic didn’t really have this problem,” he said.
Although human infections of dermatomycoses have been reported, they are rare and occur only in people who work with animals or have close contact with infected animals. One such report describes the infection of a 15-year-old girl who was attending a horseback riding camp. Two others detailed infections among tourists who rode elephants in Thailand.
The World Health Organization told STAT it was aware of the report. In an emailed statement, the agency said it believes skin mycoses are unlikely to rise to epidemic levels at this time, noting that “clusters of new or previously rare skin infections have been recorded intermittently in close contact, sexual networks and settings.”
However, the agency said the report highlights the importance for clinicians in sexual health services to be aware of unusual and emerging infections, and the need for appropriate testing when the cause of skin lesions is unknown.
Daskalakis said it would be wise for sauna operators and men themselves to practice good hygiene at saunas frequented by men who have sex with men.
“It’s a good time for these saunas to make sure they get a deep clean,” he said. “But I think this also applies to men who are attending these venues. You can try to say, ‘Don’t go to the venue,’ but that doesn’t work. We’ve known that historically. I think it’s about making sure you’re doing everything you need to do for hygiene and making sure you shower after you meet.”
