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E. coli Frequently Asked Questions

What is my risk if there is an advisory?

Most strains of E. coli are not dangerous to people. However, some can cause illness such as diarrhea, urinary tract infections, and other infections. Some infections are very mild, but others are severe or even life-threatening. More information on the health effects of E. coli can be found at the Center for Disease Control and Prevention.

During an active E. coli advisory:

  • Do not ingest contaminated water
  • Do not swim or water ski
  • Wash hands after handling fish or contaminated water

While E. coli is an indicator of fecal contamination and may not be a direct cause of illness, the threshold of 409 most-probable number of density counts per 100mL of water sample (MPN) for adopted to issue a swimming advisory relates to a risk factor of 8 illnesses per 1,000 swimmers. As the value of the MPN increases above 409 MPN, the risk of illness if exposed to contaminated waters also increases.

How can I reduce my risk of E. coli exposure?

To reduce potential health risks, you should assume all surface waters contain some E. coli whether or not it has been monitored or an advisory has been issued. This means you should make sure you do not swallow the water, or if you have touched the water, make sure to wash your hands before you touch your mouth or eyes. The single most important way to prevent person to person spread of E. coli is careful hand washing.

How is an advisory issued and removed?

Priority lakes and reservoirs are routinely monitored for E. coli. When a sample is found to be greater than the water quality criteria according to R317-2, a crew is assembled to resample the site within 24 hours or as soon as possible after the first sample. If the consecutive sample is greater than the water quality criteria, then the local health department may issue a a joint advisory. The site is routinely monitored during the advisory and will remain in place until five consecutive samples are below the water quality criteria for the site. See DWQ’s E. coli Advisory Protocol for more information.

Where is an advisory posted?

E. coli advisories are issued by the local health department following guidance from DWQ. If an advisory is in place, signs will be posted at the lake/reservoir. Contact your local health department or visit DWQ’s E. coli advisory page for more information.

Can fish from the lake be contaminated because of E. coli?

Probably not. Because fish are not warm-blooded, E. coli cannot live in the fillets. However, the water covering the fish could contain E. coli, as well as the guts of the fish. Uncooked fish may well have E. coli contamination. Wash and cook the fish, and wash your hands after handling fish and lake water to reduce your risk.

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