Minnesota Grapples with Widespread Sexually Transmitted Ringworm Outbreak
A significant public health alert has been issued across Minnesota regarding the “largest known outbreak” in the United States of a sexually transmitted form of ringworm. The Minnesota Department of Health (MDH) has confirmed that the outbreak, caused by a specific strain of fungus known as Trichophyton mentagrophytes genotype VII (TMVII), has led to over 30 suspected or confirmed cases reported in the Twin Cities metropolitan area since July 2025.
This advisory is a crucial call to action for healthcare professionals, urging them to consider TMVII in patients presenting with rashes on the genitals, perianal area, buttocks, thighs, or abdomen. Clinicians are advised to collect specimens for laboratory culture and genotyping, and to promptly report any suspected cases to the MDH.
Understanding the Threat: What is TMVII and How Does it Spread?
TMVII is a type of dermatophyte fungus responsible for causing tinea, commonly known as ringworm. These infections typically manifest as distinctive circular, red, and irritated rashes. While they can appear on various parts of the body, including the genitals, buttocks, thighs, trunk, arms, and legs, the recent outbreak has highlighted its particular propensity for sexual transmission.
Public health officials explain that TMVII spreads through direct skin-to-skin contact, with sexual contact being a primary mode of transmission. Furthermore, the fungal spores can linger on shared surfaces and personal items such as razors, sex toys, and linens, facilitating further spread. Investigations and early case studies indicate that these infections have been predominantly associated with sexual contact among men who have sex with men.
The first confirmed case of TMVII in Minnesota was identified in July 2025 in a Twin Cities resident who sought medical attention for a genital rash. Since then, the MDH and collaborating clinicians have identified a growing cluster of more than 30 confirmed or suspected cases within the metropolitan area. This escalating situation underscores the urgent need for increased clinical awareness, accurate diagnostic confirmation, and targeted prevention strategies, as emphasised by both the MDH and the Centers for Disease Control and Prevention (CDC).
Clinical Recognition and Diagnostic Approaches
The MDH has provided specific guidance for clinicians to effectively diagnose and manage TMVII infections.
Diagnostic Confirmation:
- When available, clinicians should confirm dermatophyte infections using potassium hydroxide (KOH) microscopy.
- Skin scrapings or biopsies should be obtained for fungal culture.
- Isolates from cultures should be sent for genotyping to definitively identify TMVII. The MDH Public Health Laboratory is equipped to provide confirmatory testing for these cases.
Treatment Protocols:
- For suspected TMVII cases, clinicians are advised to initiate treatment with oral terbinafine (250 mg daily) immediately, without waiting for confirmatory test results.
- Treatment should continue for a period of two weeks after all symptoms have resolved. Typical treatment durations range from six to eight weeks, with some individuals requiring up to 12 weeks of therapy.
- Topical antifungal medications can be used as an adjunct therapy for smaller lesions.
- Crucially, topical corticosteroids should be avoided as they can exacerbate TMVII infections, potentially worsening the condition and complicating treatment.
Preventing the Spread: Public Health Recommendations
Preventing the further spread of TMVII requires a multi-faceted approach involving individual vigilance and public health measures. The MDH has issued the following key recommendations:
- Avoid Close Contact: Individuals should refrain from sexual or other skin-to-skin contact if they are experiencing symptoms or have a rash suggestive of a dermatophyte infection.
- Personal Item Hygiene:
- Refrain from sharing personal items such as towels, clothing, razors, and sex toys.
- Launder clothing and linens that may have come into contact with the fungus on a high heat setting.
- Thoroughly clean shared items and surfaces with appropriate disinfectants.
- Partner Notification: Individuals diagnosed with TMVII should promptly inform their sexual partners and advise them to seek medical evaluation if they develop any symptoms.
The Minnesota Department of Health commented on the situation, stating, “The first cases of TMVII in Minnesota were identified by astute clinicians who proactively notified the health department and requested confirmatory testing… In response to several individuals seeking care and providing information on other individuals that may also have been infected, MDH established an enhanced surveillance system to identify cases in Minnesota.”
Echoing these concerns, the Centers for Disease Control and Prevention (CDC) noted in a recent update, “Over the past decade, increasing reports of severe atypical cases of ringworm have been reported worldwide. One new strain is primarily sexually transmitted. Some emerging strains cause antimicrobial-resistant infections.”
The Path Forward: Surveillance and Updated Guidance
The MDH is actively working to monitor and control the spread of TMVII. Healthcare providers are urged to continue reporting suspected and confirmed cases through the department’s online form. Submitting fungal isolates to the state public health laboratory is also critical for confirmation and to aid in ongoing surveillance efforts and the development of effective response strategies.
As more data becomes available regarding transmission patterns and optimal treatment durations, public health officials will update clinical guidance accordingly. Individuals experiencing new rashes consistent with ringworm are strongly advised to seek prompt evaluation at sexually transmitted infection (STI) clinics or primary care facilities. Open communication with sexual partners about potential exposure and symptoms remains a vital component of public health efforts to curb the spread of this challenging infection.
