Officials with San Francisco's Recreation and Park Department trying to clean up after an outbreak of what appears to be the norovirus.
Earlier this month, three campers and two employees at the park reported symptoms such as vomiting, diarrhea and nausea. Six other cases were reported in June.
About 500 people visited Camp Mather during the suspected outbreak.
The Recreation and Park Department has brought in extra hand-washing stations and is thoroughly cleaning the park to get rid of the virus.
The Centers for Disease Control and Prevention says norovirus is spread through water or when touching contaminated surfaces. It is also found in the vomit or fecal matter of infected people.
Washing hands thoroughly and proper food preparation can prevent the spread of the disease.
The Examiner says there was also a norovirus outbreak at Berkeley's Tuolomne Camp, a few miles from Camp Mather. It was closed last weekend for extensive cleaning.
Common norovirus symptoms include diarrhea, vomiting and stomach pain. It typically lasts one or two days, but can be fatal.