Virus that infected dozens likely caused by fecal matter in the lake

Swimming, boating and other water activities will resume Wednesday, July 23, at Blue Lake Regional Park in Fairview, ending an eight-day lake closure while the county investigated an outbreak of vomiting and diarrhea.

Public health officials believe the illness that infected dozens of park visitors the weekend of July 11-13 was a highly contagious norovirus, which causes flu-like symptoms that usually ends after 24 to 48 hours.

A week later, officials are now saying the lake water poses minimal risk to visitors, said county spokeswoman Julie Sullivan-Springhetti.

Dr. Jennifer Vines, Multnomah County’s deputy health officer, said the virus likely was introduced after someone had a fecal accident in the lake, and spread when swimmers and bathers swallowed the contaminated lake water.

This hypothesis is supported by interviews with parks visitors and positive norovirus tests from people who got sick.

County health officials are still waiting for final confirmation that the lake water tests positive for norovirus.

“Testing the lake water for norovirus requires pumping about 13 gallons of water through a filter,” said Vines.

Vines said, “Expert advice and common sense suggest that waiting at least a week before reopening should be sufficient from a public health standpoint.”

E. coli and blue-green algae were ruled out as the cause of the illness early on, Sullivan-Springhetti said.

Though a routine water sample collected while the lake was closed showed a high E. coli result, all other tests for E. coli have come back at low levels, she said.

The Multnomah County Health Department is monitoring the lake water for E. coli and plans to send a sample to the Centers for Disease Control and Prevention to look for traces of norovirus.

Throughout the investigation, Blue Lake remained open for other activities, including picnics, sports and a splash pad with a separate water source.

The Stumptown Half-Marathon will take place Saturday, July 26, but an affiliated triathlon at the park was canceled due to uncertainty about the lake.

When the lake reopens Wednesday, July 23, precautionary signs will ask visitors to report vomiting or diarrhea that starts within one to two days of swimming in the lake.

The signs also will remind visitors about important measures to avoid spreading illness: Don’t go in the lake if you’re feeling sick, and children under age 5 are not allowed in the lake.

Metro plans to ramp up its water testing by collecting daily samples for the next week, said Justin Patterson, parks and property stewardship program director. And Metro “will continue doing everything possible to make sure Blue Lake is a fun and safe destination for visitors,” Patterson said.

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