Mysterious Rashes, Vomiting Plague Competitors in California Tough Mudder Challenge

The county health department has issued an advisory for anyone who competed in the Sonoma County endurance event

Several people in California’s Sonoma County have fallen ill after competing in a Tough Mudder race — a collaborative obstacle course challenge in muddy terrain — on August 19 and 20 at the Sonoma Raceway.

Their symptoms were so severe, ranging from skin rashes to vomiting, that it prompted the county health department to issue an advisory.

“The Tough Mudder race involved extensive skin exposure to mud. Most affected persons have pustular rash [rashes with pus-filled blisters], fever, myalgias [muscle pain], and headache,” the advisory from the Sonoma County Department of Health Services said.

However, the advisory continued that the symptoms could have a wide range of causes — some potentially deadly.

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“These symptoms could be indicative of a minor illness called Swimmers’ Itch, but they can also indicate a staph infection or other more serious bacterial infection such as Aeromonas.”

Swimmer’s Itch is caused by microscopic parasites in water, according to the CDC, and while uncomfortable, can usually be treated at home with corticosteroid cream.

Staph infections, however, can turn deadly, the Mayo Clinic says. While symptoms vary, staph usually presents with pus-filled boils, impetigo (a painful rash), and cellulitis.

Related: 3 Dead, 1 Hospitalized from Flesh-Eating Bacteria Found in Raw Oysters and Saltwater

If the staph bacteria enters the bloodstream, it can cause a deep infection known as bacteremia, which can impact internal organs, and muscles.

While staph is generally treated with antibiotics, the Mayo Clinic points out that antibiotic-resistant strains of staph may require intravenous antibiotics.

And according to the National Institute of Health, Aeromonas is caused by “opportunistic bacteria” that generally live in water, and possess a “wide spectra of antibiotic resistance.”

The CDC says California is the first state to mandate reporting of Aeromonas infections.

“Bloodstream infections caused by Aeromonas tend to be very severe and progress rapidly,” the National Institute of Health has said. “While the overall frequency of Aeromonas as a cause of … bacteremia is low, Aeromonas bacteremia has a high fatality rate.”

The Sonoma County health department also advised: “If you participated in the race and have a rash with fever or other symptoms, please see your medical provider or, if you do not have a medical provider, your local emergency department. You may wish to take this Advisory with you. Incubation period is 12 to 48 hours.”

A TikTok video of the event showed participants assisting one another as they scaled a steep, muddy incline, and climbing in and out of murky water-filled ditches.

Related: We Tried It: Tough Mudder — a 10-Mile Run That Happens to Include 20 Crazy Obstacles

And another TikToker who participated in the Tough Mudder challenge shared a video of rash-covered knees, writing, “little did we know that chills, fever, body aches (headache) and infection would follow.”

“We hosed off, changed clothes then showered well after,” Lindsay Sirmon wrote in the TikTok caption. “After drs. visits, we are on antibiotics and topicals.”

But as Sirmon pointed out, “I mean, it is in the mud, I get that.”

PEOPLE has reached out to Tough Mudder for comment.

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