Since December 2025, about a hundred cases of dermatophilosis have been recorded in Europe, mainly among men who identify as gay or bisexual. This evokes memories of the mpox outbreak in 2022. Moreover, both diseases have inherited unsettling nicknames: “monkeypox” for the first, “mud fever” for the new one. But don’t panic, here’s what you need to know.
Its name doesn’t help to stay calm. Dermatophilosis, sometimes called “mud fever” in veterinary medicine, is actually a bacterial infection and not a scabies, which is a parasitic disease. Usually observed in animals, it can be transmitted to humans through contact with them: several cases have thus been described among farmers.
Since the end of 2025, however, nearly a hundred cases have been identified in gay and bisexual men in Europe, suggesting human-to-human transmission. According to a report published on Wednesday, June 17, by the European Centre for Disease Prevention and Control (ECDC), most of the people affected had frequented saunas in the days preceding symptom onset. This echoes the scenario that preceded the mpox outbreak (“monkeypox,” renamed mpox) that affected gay and bisexual men during the summer of 2022… But the comparison ends there: it is a benign infection, easily treatable and whose spread remains limited at this stage. Explanations.
What is dermatophilosis?
Dermatophilosis is a skin bacterial infection caused by the bacterium Dermatophilus congolensis. It is well known to veterinarians because it mainly affects animals, particularly cattle or horses exposed to humid environments. “Some cases of animal-to-human transmission following identified contact had been described but no human-to-human transmission had hitherto been demonstrated”, explains Dr. Maxime Bonjour, who identified the first cases in Lyon at the end of 2025, where he coordinates the CeGIDD at the Croix-Rousse hospital.
The data collected in Spain and France, where 40 cases have been recorded in eight cities, now suggest human-to-human transmission. “Most of the men concerned reported having frequented saunas and having sexual encounters there”, repeats the public health physician, who immediately adds: “This is not a sauna disease.” Cases have indeed been observed in people who did not frequent this type of establishment, which mainly provides a favorable environment due to close contact and humidity. The ECDC also reports several cases in Norway linked to the practice of martial arts, another context generating close contact.
Is dermatophilosis an STI?
Because human-to-human transmission appears to occur via close contact, this includes sexual relations. However, dermatophilosis does not seem to be transmitted through sexual fluids but through direct skin-to-skin contact. “We are talking about a dermatological condition that is sexually transmitted by skin-to-skin contact”, explains Dr. Bonjour. Condoms therefore do not constitute an effective means of prevention against this infection. The ECDC notes that transmission via contaminated surfaces, for example when sharing towels or linens, remains possible but has not been demonstrated to date.
What are the symptoms of the disease?
Benign, dermatophilosis causes skin lesions that can resemble those of other dermatological conditions: crusts, pustules or papules. These typically appear a few days after contact and are most often located in the pubic area, the testicles, the penis, or the anal region. Lesions can also be observed around the mouth, on the chest, arms, buttocks, or inside the thighs.
These lesions can itch, but are mildly or not painful and do not seem to leave scars. “No serious cases, nor even visits to the emergency room, have been recorded”, notes Maxime Bonjour. In cases observed so far, the disease generally does not accompany significant general symptoms.
At this stage, no more severe form has been observed in people living with HIV on treatment. Researchers still lack data regarding people who are highly immunocompromised.
How is dermatophilosis treated?
Dermatophilosis is easily treated. “This bacterium responds very well to antibiotics such as amoxicillin”, says Maxime Bonjour. In some cases, local treatments may even suffice. “One of our patients did not want antibiotics and only benefited from local antiseptic care: the lesions also regressed”, reports the physician. The ECDC also mentions several cases of spontaneous recovery.
What should you do if you have symptoms?
If unusual skin lesions appear, Maxime Bonjour recommends promptly consulting at a CeGIDD or a sexual health center. Samples will allow verifying that it is indeed Dermatophilus congolensis and not another skin condition or an STI requiring different management.
How to prevent the infection?
Prevention relies primarily on simple hygiene measures: avoid close contact with people who have suspicious skin lesions, do not share towels or toiletries, and regularly wash your hands as well as the affected areas with water and soap. For Maxime Bonjour, the situation does not justify either exceptional measures or major changes in behavior: “There is no need to fear going to the pool or saunas, provided you follow the usual hygiene rules.”
Should we worry about an outbreak of dermatophilosis?
For Maxime Bonjour, the answer is clearly no. “We are not facing a scenario comparable to mpox in 2022. This is a benign skin infection, easily treatable and with no serious cases identified at this stage, he reassures. We are also not faced with significant epidemic surges that would suggest an escalation comparable to what was observed during the mpox outbreak.”
In other words, while this infection deserves monitoring and better documentation, the available data do not suggest either high clinical severity or a transmission dynamic comparable to that observed during the mpox outbreak of 2022. At this stage, dermatophilosis appears more as an emerging infection to monitor than as a new health emergency.
