Mystery outbreak in California sees ‘hundreds’ of people break out in rashes and suffer vomiting after competing in Tough Mudder event

Hundreds of people who competed in a Tough Mudder run last weekend have been struck down by mysterious symptoms.

Participants have reported rashes, fever, headache, muscle aches, nausea and vomiting 24 hours after competing in the event that sees thousands race through an obstacle course involving climbing and crawling through mud, and swimming waist-to-neck-deep in water.

The County of Sonoma Department of Health Services in California fears it may be the result of a parasite that lives in mud, known as the schistosomatid trematode flatworm, or Staph, a nasty bacterial infection that can lead to vomiting and fever.

At least 350 people are thought to have symptoms after taking part in a Tough Mudder race at Sonoma Raceway on August 19 and 20.

The health department advised people who took part in the race who have a rash with fever or other symptoms to see their medical provider.

Participants have reported rashes, fever, headache, muscle aches, nausea and vomiting 24 hours after competing in the event

Nicole Villagran showed her rash, which covers both arms and the sides of her body

The rash is also on her legs after she took part in the muddy obstacle course 

Participants slog through the mud mile obstacle during the Tough Mudder endurance challenge at Raceway Park in Englishtown, New Jersey, US, in November, 2011. At least 350 people are thought to have symptoms after taking part in a Tough Mudder race at Sonoma Raceway in California on August 19 and 20 2023.

The Sonoma health department said the symptoms could be a minor illness called Swimmer’s itch, a Staph infection, or a more serious bacterial infection such as Aeromonas.

Swimmer’s itch, also known as cercarial dermatitis, is caused by a parasite that lives in waterfowl and snails, which causes an itchy rash and raised red bumps. 

People can get symptoms when the parasite penetrates the skin after being in contaminated water. 

According to the Centers for Disease Control and Prevention, small reddish pimples may appear within 12 hours of being in water, which may turn into small blisters.

Sonoma health officials also said it could be a Staph infection or a more serious bacterial infection such as Aeromonas.

Staph infections are caused by staphylococcus bacteria and can cause boils and oozing blisters. However, Staph is not found in dirt or mud but can be spread through direct skin-to-skin contact.

In rare cases, Staph infections can turn deadly if the bacteria invade deep into the body or enter the bloodstream, which can lead to fever and muscle pain.

Aeromonas is caused by aeromonas hydrophila bacteria. Symptoms include watery stools, mild fever and vomiting because it can result in infections of the stomach area. 

Aeromonas has a fatality rate ranging from 28 percent to 46 percent. 

One participant told ABC 7 Bay Area: ‘I look like I have a severe rash on both sides [of my body].’ 

Curtis Vollmar, a Tough Mudder participant, said his rash had mainly gone, but he said, ‘from the elbows up and the knees down, I was just covered in these pimply, red, blister type things.’

He told KGO TV that 12 of the 13 people he did the event with also suffered symptoms, but they are fading.

Another participant, Ashwin Chatwani, said: ‘We have an email chain out to the Tough Mudder organization and it seems there’s been 350 plus people and counting that have been affected by the incident.’ 

Tough Mudder said it was ‘taking all necessary steps to fully investigate the matter.’