ARS TECHNICA – Hundreds of people who participated in a recent Tough Mudder event—a very muddy obstacle course race—held in Sonoma, California, have fallen ill with pustular rashes, lesions, fever, flu-like symptoms, nerve pain, and other symptoms, local health officials and media outlets report.
The cases could be caused by various infectious agents, including Staphylococcus bacteria, but the leading culprit is the relatively obscure Aeromonas bacteria—specifically A. hydrophila, according to the Sonoma County health department.
In a statewide alert this week, the California Department of Public Health said it is considering it an Aeromonas outbreak, noting that multiple wound cultures have yielded the hardy bacterium.
A spokesperson for the Sonoma County health department told the Los Angeles Times on Thursday that, based on calls and emails the department had received, health officials estimate that the outbreak involves around 300 cases. Tough Mudder participants, meanwhile, have tallied as many as 489 cases in online forums.
The Tough Mudder event was held at the Sonoma Raceway on August 19 and 20, 2023, with symptoms of infection developing in cases within 12 to 48 hours afterward.
The Sonoma County health department advisory noted that the race “involved extensive skin exposure to mud” and that participants with a rash, fever, or other symptoms should go to their health care provider or, if no provider is available, to a local emergency department.
While Tough Mudder events, held all around the country, challenge participants to be rugged and resilient as they traverse mucky obstacles, the toughest mudder is, without question, A. hydrophila.
This is a rod-shaped, gram-negative bacterium that lives in aquatic environments and soil. It infects almost everything—humans, animals, birds, fish, and marine reptiles, according to a pathogen data sheet from the Canadian government. And it can be found almost everywhere—water, soil, mud, fresh produce, meat, and dairy products …
BETH MOLE is Ars Technica’s Senior Health Reporter. Beth has a Ph.D. in microbiology from the University of North Carolina at Chapel Hill and attended the Science Communication program at the University of California, Santa Cruz. She specializes in covering infectious diseases, public health, and microbes.