It’s the time of year when people take to the water to relax and beat the heat, but unfortunately, noroviruses don’t mind getting wet. Over the weekend, three popular swimming spots were closed after visitors became sick with norovirus-like symptoms: Horseshoe Lake in Washington, Blue Lake in Oregon, and Eagle Island State Park in Idaho.
At Horseshoe Lake, the public park and swimming area was closed on Monday and will remain closed until at least this Friday. There had been 202 reported cases as of Tuesday, at a park that regularly has 2,500 visitors a day this time of year.
Health officials tested the water and found it safe in regards to bacterial levels. Due to its popularity, Horseshoe Lake already has its water tested on a weekly basis. Health officials did find the bathrooms to be in suboptimal condition, but these were not likely the source of the outbreak, and the park’s septic system was not a concern. The health district has also been talking to the visitors, and currently, everyone who has become sick swam in the lake between July 10th and July 13th. The health department is also attempting to isolate viruses in water samples, in addition to testing two stool samples from sick patrons, and is working with the CDC to determine the cause of the outbreak.
The Blue Lake Regional Park similarly closed its swimming area on Monday after visitors began getting sick over the weekend. Tests on the lake water ruled out E. coli, making health officials suspect norovirus based on the symptoms. According to the county health department, at least 25 people have become sick after being in the water.
Over 100 visitors to Eagle Island State Park over the weekend also unfortunately experienced gastrointestinal illness, and test results confirmed norovirus as the culprit. The swimming areas will be closed for two weeks, while it is drained and refilled.
In each case, the most likely source is a sick visitor, particularly someone who swam, and maybe even passed stool or vomit into in the lake. The public health officials investigating the outbreaks are asking people to avoid the water, and for those who became ill to report this information, as well as seek medical care if needed.
UPDATE: Norovirus was found among those who got sick at Horseshoe Lake, though the water tested negative. The lake reopened July 19th.