The cause of the deadly outbreak of Legionnaires' disease in Hopkins last month was a cooling tower at a local juice company.
The Minnesota Department of Health said Wednesday test results confirmed a strain of Legionella bacteria (which causes Legionnaires' disease, a lung infection) was found in one of the cooling towers at Citrus Systems, Inc., located at 415 11th Ave. S. in Hopkins.
"The lab testing is highly specific and provides us with great confidence that this tower is the source of infection," MDH deputy state epidemiologist Richard Danila said in a statement.
Officials stressed that although the bacteria was discovered in the cooling towers, products made and packaged at Citrus Systems are not affected or involved in the outbreak.
No new cases reported
The outbreak made 23 people sick – 17 of them were hospitalized, and one person died.
There haven't been any new cases of Legionnaires' disease reported since Sept. 22, and health officials are pretty confident no new cases will be reported.
"Although it’s been more than 14 days since the tower was sanitized and since our last case, which is beyond the typical 10-day incubation period for Legionella, it’s still possible we could see an additional case if someone were exposed on Sept. 27," Danila said. "It often takes time for cases to present for care and be tested. However, we believe the source has been identified and remediation has occurred."
How did the outbreak happen?
Cooling towers (air conditioning units for larger buildings) are a common source for Legionnaires' disease. The bacteria can grow in the water system, and when the contaminated water is turned into mist by the cooling system and released into the air, it can make whoever breathes it in sick.
"We don’t know in this case exactly what went wrong to cause the build-up of Legionella," Danila said. "This situation clearly demonstrates how difficult it can be to keep systems free of Legionella, even when they are well-maintained."
The Minnesota Department of Health says Citrus Systems has cooperated with their investigation, and has cleaned and disinfected its towers. It is also working with the health department to make sure their cooling system is working correctly.