In March 2020, the Minnesota Department of Health (MDH) foodborne and waterborne illness hotline received an online complaint reporting that multiple people had become ill with coughing and difficulty breathing within seconds of the spa pool jets being turned on at a hotel in Duluth on March 1. Although the complainant was the only person interviewed, he reported that multiple other individuals experienced similar symptoms.

MDH sanitarians conducted an inspection of the spa pool on March 3. It was observed that the spa pool emergency shut off button was on the same control box as the button to turn on the jets. Pool operators said that despite being labeled, there was a history of spa pool users pushing the emergency shut off button. On February 29, the shut off button was accidentally pushed by a pool user allowing the water to sit in the spa pool overnight without circulating. On the morning of March 1, the pool operator checked the chemicals and stated they were where they should be. No measurements for combined chlorine was noted. However, an employee failed to notice the pump was not working. The spa pool opened at 8:00 am. Complaints were received starting at 8:30 am.

As a result of this outbreak, the hotel updated their testing instructions and retrained staff. Additionally, a flip cover was installed over the emergency shut off button.