In a follow-up to the Legionnaires’ disease outbreak in Hopkins, Minnesota, state health officials report three additional confirmed cases in people who live, work or spent time in Hopkins, bringing the total to 23.
The pattern of where cases were likely exposed is consistent with a community-wide exposure to contaminated water that became aerosolized, most likely from a cooling tower. Extensive interviews with Legionnaires’ cases and/or family members did not identify a common exposure – such as a restaurant or a store or specific building — other than living, working, or spending time in Hopkins.
To date, seven locations with one or more cooling towers have been identified by Hennepin County Public Health and the City of Hopkins, in collaboration with the Minnesota Department of Health (MDH), as being possible sources. As of Sept. 29, all of these cooling towers have been or are being remediated by their owners.
Environmental samples from cooling towers within the area of concern have been collected. These tests are in process. Legionella is a slow-growing bacteria and testing for the bacteria in the laboratory can take weeks.
While the remediation of known cooling towers is important in reducing any ongoing risk to people in the area, MDH will not consider the investigation complete until all nearby cooling towers that could be a source of the Hopkins illnesses are identified and remediated, and no additional cases are identified.
It’s important to note that cooling towers are not regulated in Minnesota and therefore no state or local registry or master list of cooling towers exists, making identification difficult. Building owners are responsible for operating cooling towers consistent with industry standards.
Minnesota and many other states have seen an increase in the number of Legionnaires’ disease cases in recent years. From 2012 through 2015, Minnesota had an annual total of 50-58 confirmed cases of Legionnaires’ disease. To date in 2016, more than 90 cases have been reported. Most cases of Legionnaires’ are reported in later summer and early fall.
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