By Samuel Hansen

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Residents of Portland and miscellaneous service areas are once again facing the emerging reality of Cryptosporidium in their drinking water. The Portland Water Bureau has announced the detection of a single Cryptosporidium oocyst in a 50-liter sample from the Bull Run Watershed collected on September 28; no detection was made in the subsequent sampling on September 30. Prior occurrences saw the last detection back in April 2025. This microscopic parasite, while typically low-risk for those with robust health, could pose a serious threat to individuals with compromised immune systems.

The public has been duly assured, as per the Portland Water Bureau’s recent update, that there’s no urgent call for additional precautions. However, the city is already required to begin treating for Cryptosporidium and is mandated to have a filtration system in place by September 2027. It seems the Bureau is actively working to rapidly and consistently monitor the presence of the parasite until such measures are functional.

The threat of cryptosporidiosis is real but varies in severity. Exposure to the organism can induce symptoms including diarrhea, vomiting, and fever, mainly in the immunocompromised population. Considering this potential hazard, the Centers for Disease Control and Prevention urges those at risk to consult healthcare providers about the safety of the water prior to consumption. This is particularly critical for individuals diagnosed with conditions like AIDS, hereditary immune disorders, cancer, and transplant recipients who are on immunosuppressive medication.

The Portland Water Bureau services multiple districts, including, but not limited to, Burlington, the City of Gresham, and the Tualatin Valley. Water consumers are encouraged to verify whether their water supply is sourced from Bull Run by reaching out directly to their local water providers. For those seeking to closely monitor the situation or ensure their water is free from Cryptosporidium, the Bureau has committed to continuously publishing all testing outcomes on the city’s website and notifying the public should any risk become apparent.