MYSTERY: More than 200 get sick after swimming at Kitsap County lake


PORT ORCHARD, Wash -- A popular lake in Kitsap County will remain closed at least until Friday as public health officials investigate why hundreds of people reported coming down with a norovirus-type illness after swimming there.

The Kitsap Public Health District and Kitsap County Department of Parks and Recreation temporarily closed Horseshoe Lake County Park on Monday morning. Initially some 80 people had reported illnesses after swimming at the park, but that number has risen dramatically.

The Kitsap Public Health District said that as of 4 p.m. Tuesday, the Health District has received over 200 reports of people getting ill after swimming at Horseshoe Lake County Park between  last Thursday and Sunday.

"Based on interviews with affected people, the main symptoms being reporting are vomiting, diarrhea, and stomach cramps," the district said in a news release. "The onset of the illness is approximately four to 24 hours after swimming at the park, and the duration of the illness is approximately eight to 36 hours after the first signs of illness begin. Not all people who swam at the park during this period have become ill, and most of the people who were there have recovered."

The district said, "At this point, bacteria do not appear to be the source of the illnesses. Lake water samples for E coli bacteria that were collected on Monday morning were well below health threat levels ... drinking water samples from the park were also within acceptable levels and came up negative for the presence of bacteria. Based on reported symptoms and onset/duration of illness, the Health District still believes that a virus is the likely source of the illnesses."

Tests show bacteria levels in the lake are well below closure levels, the district said. Health officials say this supports their working theory that some kind of virus is causing the illnesses.

"With the help of the Centers for Disease Control in Atlanta, Georgia, the Health District will be collecting additional water samples from the park’s swimming area to be analyzed for viruses at the federal CDC laboratory," it said.