Rare skin infection investigated after cluster of cases linked to same gay sauna

Health officials are investigating a rare skin infection after a cluster of cases among gay and bisexual men in France was linked to a single sauna.

The outbreak first came to light after nine men sought treatment at the sexual health clinic at the University Hospital in Lyon between December 2025 and February 2026. All had sex with other men, while seven reported visiting the same gay sauna before developing symptoms.

Researchers say the infection, dermatophilosis, is caused by the bacterium Dermatophilus congolensis, which is normally found in animals. Human infections are rare and have traditionally been associated with direct contact with livestock.

Seven men had visited the same gay sauna before falling ill

None of the men in the French cluster lived in rural areas or reported contact with farm animals, according to a study published this month in the CDC journal Emerging Infectious Diseases. Most developed lesions on parts of the body “exposed during sexual contact.”

Symptoms included red bumps, pustules, scabs and scaly patches affecting areas including the genitals, torso, legs and beard. All nine men responded well to antibiotic treatment.

Seven patients said they had visited the same sauna in the Lyon area before falling ill. Another reported visiting three bathhouses in Paris, while one said he had not attended any saunas.

Although doctors were unable to prove direct sexual contact between the men, genetic analysis showed the bacterial samples were closely related. The study’s authors wrote: “Although no direct sexual contact between patients could be formally established, the … overlapping sexual exposures, shared multiple STI history, lesion distribution, and close genomic relatedness of isolates strongly support transmission occurring within shared exposure networks, likely involving close physical or sexual contact.”

Cases have since been reported across Europe

One patient returned eight weeks after completing treatment with signs of another infection. He told doctors he had revisited the same sauna, leading them to suspect reinfection rather than a relapse.

Researchers also suggested that “evolving sexual practices in the [PrEP] era could lead to emergence of new transmissible” skin infections.

Since the French cases were identified, further infections have been reported elsewhere in Europe. The European Centre for Disease Prevention and Control (ECDC) said 70 cases have now been recorded across France, Germany, Spain and Sweden, with many patients reporting visits to sex-on-premises venues, including adult spas. Cases have also been identified in Norway among people involved in martial arts.

The ECDC said the overall risk to the wider public remains low, but noted that the outbreak may point to a change in how the infection spreads, with close physical contact thought to be the most likely route. It has urged clinicians to consider dermatophilosis when investigating unexplained skin lesions and stressed that public health messaging should avoid stigma.