California health officials have issued an advisory after several people who participated in a Tough Mudder race last weekend got sick. 

Nearly two dozen people who ran in the Tough Mudder challenge at Sonoma Raceway on August 19 and 20 developed rashes with fever and reported muscle pain or nausea and vomiting, according to the Sonoma County Department of Health Services. 

"The Tough Mudder race involved extensive skin exposure to mud. Most affected persons have pustular rash, fever, myalgias, and headache," health officials said. "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." 

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Athletes who competed in the race crawled through mud and water and climbed over and under obstacles like a barbed wire fence. Several contestants posted about their condition after the race on social media, complaining of a red rash with puss, fever and body aches.

"Anywhere on my body that touched the ground had red spots," participant Chris Palakos told local FOX affiliate KTVU. 

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Tough Mudder participants shared pictures of their rashes with KTVU. The images show their arms and legs covered in infectious sores. 

At least 22 people contacted the Sonoma County health department to report rashes, interim health officer Dr. Karen Smith said. Officials believe people likely contracted a bacterial infection called aeromonas, which is a bacterium that lives in water and is contracted through open wounds. It is not contagious. 

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"We want to be sure to let people know . . . if you attended this event, and you have a rash, fever, aches, we want you to go see your doctor," she told KTVU. 

Smith said that one person who saw an infectious disease specialist tested positive for aeromonas bacteria. The infection is commonly misdiagnosed as a staph infection or swimmer's itch — a skin rash caused by an allergic reaction to certain microscopic parasites that infect some birds and animals, according to the Centers for Disease Control and Prevention.

"We want doctors to have the right information, so they know which things to consider, staph being one of them," Smith told KTVU. "But what we don’t want to happen, because it looks like staph, we don’t want them to just treat for staph and find out it’s something else."

Sonoma County health officials encouraged anyone who participated in the race and later developed a rash to see a doctor or, if they do not have a medical provider, to contact their local emergency department.