Oct. 29 Water Update | E. coli lab test results available

Officials say it's not possible to determine connection of E. coli illness to Island water

Public Health – Seattle & King County has been keeping track of reports of E. coli illness that could be related to Mercer Island water, after bacteria was discovered in the Island’s water supply last month.

Public Health reported a presumptive case of illness in an Island resident on Sunday Oct. 5. Results of lab tests ordered to identify the strain of E. coli that sickened the patient, and to determine whether the illness was water-related, have recently become available.

The patient was confirmed to have HO157:H7 E. coli, which can cause gastrointestinal illness, but none of the water samples revealed contamination from the HO157:H7 strain.

The patient did not require hospitalization and has since made a full recovery, according to a city press release.

“With just one patient, it is not possible to confirm or deny a connection to the water system with absolute certainty, but many other sources of E. coli contamination do exist in the environment, and 20-30 patients contract E. coli in King County each year for a variety of reasons,” according to the release.

The findings, as well as more complex lab tests performed on the water supply, also revealed that no unusual clusters of illness were detected among Island residents.

“It’s possible that other people reported illness to their doctors, but not to Public Health,” said city communications manager Ross Freeman.

Freeman said that doctors can do a simple test in their office. The Island resident was determined to be a “presumptive case” after this test, and went through a more involved testing process overseen by Public Health.

“With only one patient, it’s hard to issue a blanket statement,” Freeman said.

Mercer Island is continuing a vigorous water quality monitoring program, testing as many as 16 water samples a day. All of the 400 samples tested since Oct. 2 have been found free of E. coli and Total Coliform bacteria.

The city, working with the state Department of Health, issued ‘boil water’ advisories in late September and again in early October after E. coli and Total Coliform bacteria were detected in routine water quality monitoring samples at several different locations in the city’s water system.

The last advisory was lifted almost three weeks ago on Oct. 8, following multiple days of clear test results, and with additional inspection protocols and boosted chlorination levels in place.

Since the end of the incident, the city and the Chamber of Commerce have launched a “Dine Local” campaign to encourage community support of restaurants impacted financially by the incident. More information is available at: www.mercergov.org/dinelocal

The city will share the results of expert review from water system specialists Confluence Engineering Group at a City Council meeting on Nov. 3. 

Based on its experience with emergency communications during the incident, the city has already begun to implement a number of improvements to notification systems, email software and other mass-outreach technologies.