A Tough Mudder competition in California’s Sonoma County may have sickened hundreds, according to an updated report on the event, where participants claimed they smelled cow manure on the muddy, wet field.
“There was a few times during the race where I could smell cow manure,” Nicole Villagran, who developed a rash after participating in the event, told ABC News.
“You wake up the next day and you’re like, ‘What is all this on my arm? Like, what is going on here?’ And it’s on both arms. That’s where I was digging and doing army crawls and it’s on the inside of my knees where I was pushing off of as well,” said Villagran.
A Tough Mudder race is a collaborative obstacle course challenge, where participants attempt Boot Camp-style hurdles in mud and muddy water.
TikToker Lindsay Sirmon, who participated in the Tough Mudder challenge, shared a video of rash-covered knees, writing, “Had a blast at Tough Mudder Sonoma but…..little did we know that chills, fever, body aches (headache) and infection would follow.”
“We hosed off, changed clothes then showered well after,” 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.”
ABC News reports that now at least 350 people who participated in the August 19-20 event have become sick.
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 August 23 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, although there have been no reports of fatalities from the Sonoma County event.
“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.
Tayfun Coskun/Anadolu Agency via Getty
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.
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 representative for Tough Mudder said in a statement to PEOPLE that all participants and spectators from the event have been contacted and urged to seek medical attention if they are experiencing any symptoms. Additionally, they are working closely with the County of Sonoma Health Services to investigate the matter.
“As it has been for the thousands of races we have put on for millions of racers across the globe, the health and safety of the Tough Mudder community is always our top priority,” the statement said. “All necessary protocols were followed in preparation for, and during, the event. Our thoughts are with those affected and we are actively investigating to understand exactly what occurred.”
PEOPLE has reached back out to Tough Mudder for further comment.