On Friday, the Portland Water Bureau received results that Cryptosporidium was detected in a routine water sample collected Monday, January 2, from the Bull Run watershed, which provides drinking water to Portland and neighboring communities. The lab results show that two individual Cryptosporidium oocysts were present in a 50-liter (~13 gallons) sample of water.


At this time, we do not believe there is any public health risk as a result of this detection. The public is not being asked to take any precautions.

The Portland Water Bureau currently does not treat for the parasite because of a variance issued by the State of Oregon Health Authority (OHA) in 2012. Instead, the Portland Water Bureau is required to conduct routine monitoring for Cryptosporidium and notify the public of any detections.

* The Portland Water Bureau tests at least 100 liters per week from the source water intake for Cryptosporidium, a potentially pathogenic microorganism.
* This detection at the intake is the first since the Portland Water Bureau began operation under the variance in April 2012 and the first since December 30, 2011, when a single oocyst was also detected. These two instances are the only detections that have occurred since August 2002.
* As required by the conditions of the treatment variance, the Portland Water Bureau will begin increased monitoring next week at the source water intake for at least one year to demonstrate whether the Cryptosporidium concentration is less than 0.075 oocysts per 1,000 liters.

“Laboratory results indicate a detection of an extremely small amount of Cryptosporidium,” said Water Bureau Administrator Mike Stuhr. “The Water Bureau will increase monitoring at the drinking water source, as we agreed to do as a condition of the variance. The variance continues to be valid despite this single detection.”

The City has consulted with the Multnomah County Health Department and OHA. Public health officials have determined that no special precautions for Portland’s drinking water are currently necessary, aside from increased monitoring and testing efforts currently underway. As is always recommended, people with severely weakened immune systems should seek specific advice about drinking water from their health care provider.

“Since animals can carry certain types of Cryptosporidium, if we test enough water we will eventually find this parasite, even from a highly-protected source like the Bull Run” said Multnomah County Health Officer Dr. Paul Lewis. “Fortunately we have never had an outbreak of Cryptosporidium in the 120 years we have been drinking water from the Bull Run.” The county’s ongoing surveillance has shown no unexplained increase in Cryptosporidium cases.

The Water Bureau is performing a thorough investigation that may include additional sampling and will attempt to identify any possible sources of the Cryptosporidium detection. The Water Bureau will notify the public of any additional detections.