E coli ruled out as cause of Blue Lake illness, norovirus suspected

July 15, 2014

The Multnomah County Health Department is working closely with Blue Lake Regional Park officials to investigate reports of diarrheal illness from people who visited the lake July 12 and 13

Park officials closed the lake to swimming Monday, July 14, after two families reported several people in both parties having a combination of diarrhea, vomiting, rash and cramps.  Staff at the Health Department's Communicable Disease program are continuing to talk to park visitors to determine what kind of diarrheal illness this is and whether it can be traced to swimming in the lake.

Officials ruled out E coli as a possible cause today. E coli bacteria was not detected in water samples taken Monday from both the shallow swimming area and deep areas of the lake.  Routine twice-weekly tests leading up to the weekend also showed levels below those considered to be a risk to swimmers. In addition, no toxic algae blooms have been observed.

“Our initial impression is that the illness is due to norovirus or a similar stomach virus,” said Deputy Health Officer Dr. Jennifer Vines.

Norovirus is the most common cause of vomiting and diarrhea.  There is no treatment and most people recover in 24 to 48 hours.  The very young and elderly can suffer dehydration as a complication.  “Anyone with these symptoms should be sure to drink plenty of fluids and contact their health care provider with any concerns,” added Dr. Vines.

Viruses and bacteria that cause diarrhea can be transmitted in shallow lakes when someone who is ill sheds stool in the water.  Other swimmers can inadvertently swallow contaminated water and become ill.  Park officials take precautions to promote water flow and minimize risk to bathers. 

The Health Department will continue to work closely with park officials to determine when it is safe to re-open the lake to swimming and boating. To learn more, call the  Multnomah County information line at 503-988-4454.