Public Health investigating possible outbreak at a Lake Sammamish swimming beach

Update 9/2/16

Tibbetts Beach at Lake Sammamish is approved to reopen.

Public Health is aware of 15 people who got ill after swimming at Tibbetts Beach on Friday, August 26th. Based on their symptoms, the timing between when they swam and became ill, and the duration of illness, we suspect that the likely cause was norovirus. In addition to those who got ill after swimming, two additional people got sick: while they did not go in the water, they were household members of people who did. These ‘secondary cases’ happen frequently with norovirus. Norovirus is a common and very contagious virus spread through food, water, and via surfaces like door knobs and tables, and is easily transmitted from person to person.

As part of our investigation, Public Health and our partners tested samples of water from the beach for norovirus, as well as other indicators of fecal (poop) contamination and for toxic algae. All of these tests came back negative, providing reassurance that there does not appear to be an ongoing risk of illness associated with swimming in the lake.

This is a good reminder not to swim in a public venue – whether pool or lake – when you have a diarrheal illness, and to make sure that babies wear leak-proof diapers. Showering before using public recreational water facilities is also an excellent idea. Anyone who is suspected of having norovirus should take the utmost care to wash hands carefully to minimize risk of spread to others. And households that have people ill with norovirus may want to pay special attention to cleaning and disinfection. Proper methods to disinfect norovirus may be found here.

Update: 8/30/16 at 5:53 p.m.

Water samples from Tibbetts Beach at Lake Sammamish are being tested for several different organisms as part of our investigation into the cause of the illnesses. This afternoon, test results came back from the King County Department of Natural Resources and Parks (DNRP) laboratory that showed fecal coliform below the level of concern. This information is posted on the DNRP swim beach testing website. We are waiting for results from tests for other organisms to come back and will update this blog with the information when it’s available.

Update (8/30/16):

At this point in time, all illnesses that have been reported are associated with the specific swimming location of Tibbetts Beach. We have not received any reports of illness associated with other beaches along the lake. Because of this, Public Health is not recommending closure of other beaches along the lake.

The King County Department of Natural Resources and Parks collected samples on Monday from the following locations around the lake:

–          Tibbetts Beach

–          Tibbetts Creek

–          Idylwood Beach (taken as part of routine sampling)

Results should be available later this week, and will be posted here.

Original (8/29/16):

Public Health – Seattle & King County received a report today of up to 15 children becoming sick with vomiting and diarrhea after swimming at Tibbetts Beach on Lake Sammamish State Park on Friday, August 26. We are in the very earliest stages of investigating this possible outbreak, and do not yet know specifically what type of organism caused the illness.

Symptoms occurred within 24 hours of the Friday beach visit. At this point in the investigation, we have no reports of hospitalizations or ongoing illnesses. Norovirus is suspected, based on the symptoms, the time between exposure and symptoms developing, and the length of the illness, though we are looking into other potential causes based on the reported symptoms.

Temporary closure

Out of an abundance of caution, Public Health has advised to temporarily close Tibbetts Beach at Lake Sammamish State Park. (Sunset Beach is closed due to construction.) Washington State Parks is posting signage today to indicate the closures.

Further investigation

Our next steps include:

  • Public Health Environmental Health staff has done a walk through at the beach this afternoon with Washington State Parks.
  • Public Health disease investigators are contacting people who reported ill family members to interview them. These interviews, which include detailed questions about symptoms and onset and length of symptoms help us narrow down potential sources of illness.
  • Our sister agency, the King County Department of Natural Resources and Parks, is conducting water sampling for bacteria and algae toxins today, which may help in the investigation.

Hundreds of people were using the park over the weekend, but only a handful of people reported illness. Anyone experiencing diarrhea for more than three days after swimming at Tibbetts Beach over the weekend is encouraged to talk with their health care provider.

Help prevent water-borne illness

If you have diarrhea or vomiting, or had it recently, wait two weeks after symptoms end before swimming in beaches and pools and going in spas. Your fellow swimmers thank you.

We will update this blog when more information is known.

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3 thoughts on “Public Health investigating possible outbreak at a Lake Sammamish swimming beach

  1. We know 2 kids who had to be on a drip at the emergency room due to dehydration after falling ill. All members of their party got sick. It spread from the kids to adults, as they got sick a few days later. This has to be something other like Norovirus.

    1. We are so sorry to hear about these ill children. If they believe they were ill due to exposure to the water at the lake, they should call Public Health’s Communicable Disease and Immunization Section at 206-296-4774. Thank you!

      1. Ok, we will tell them. It was 3 families, and the ones who were at the lake, all got sick within the first 24 hours, and it spread to some of the adults later in the week.

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