Suspected human-to-human sexual transmission of dermatophilosis

Published on

15/06/2026 - 19:08 GMT+2

According to a study published (source in French) by a team of epidemiologists from the Hospices Civils de Lyon (HCL) in the US journal Emerging Infectious Diseases in early June, dermatophilosis may have been transmitted from human to human through sexual contact.

Also known as “mud fever”, this bacterial zoonosis, rare in humans, had until now only been observed in farmers or riders in contact with infected horses or cattle.

Around forty cases in France and Spain, including about thirty in Lyon, were recorded between January and June. The published study focused on nine patients who came to HCL for consultations. Seven of them reported having had sexual intercourse in gay saunas in Lyon, sometimes the same ones, in the days preceding the onset of lesions.

Although no links between members of the cluster were established, the researchers nevertheless believe that “genomic similarity and shared sexual exposures strongly suggest human-to-human sexual transmission of this zoonotic bacterium.” All are “men who have sex with men in Lyon and Paris.”

Antibiotic treatment

The symptoms seen in infected patients are pustules and crusts on the skin, around the genital area, on the torso, around the mouth and on the lower limbs.

While in animals these superficial lesions can progress to a widespread, potentially fatal form, no patient was hospitalised. A simple antibiotic treatment, “sometimes combined with topical antiseptic care”, led to rapid improvement.

Transmission, most likely via skin-to-skin contact, is thought to have been exacerbated by the humidity and heat in saunas. This is believed to have promoted the release of zoospores, bacteria that can move through water and penetrate the epidermis.