Researchers Conclude Legionnaires Outbreak Linked to Change in Water Supply

Flint, Mich. – A research team with the Flint Area Community Health and Environment Partnership (FACHEP) has found that the majority of Legionnaires’ disease cases that occurred during the 2014-15 outbreak in Genesee County can be attributed to the change in the City of Flint’s drinking water supply to the Flint River.

The team’s findings are based on detailed statistical analysis of multiple datasets. The researchers also found that the specific strain of Legionella isolated from Flint residences as part of FACHEP’s sampling in 2016 is not readily detected by common diagnostic tests for Legionella. These conclusions are part of two peer-reviewed scientific reports authored by FACHEP and recently published in the academic journals Proceedings of the National Academy of Science (PNAS) and mBio.

The researchers conducted an exhaustive analysis of data on Legionnaires’ cases in Genesee, Wayne and Oakland Counties from 2011 to 2016. FACHEP researchers determined that in 2014-15 there was an increase in the risk of acquiring Legionnaires’ disease across the Flint water distribution system that is consistent with a systemwide proliferation of Legionella bacteria. An estimated 80 percent of Legionnaires’ cases during this period are attributable to the change in water supply, according to the article in PNAS.

“During the period when their water was supplied from the Flint River, Flint residents were seven times more likely to develop Legionnaires’ disease,” said lead author Sammy Zahran, professor of economics at Colorado State University. “After public announcements urging residents to boil their water, there was a lower risk of developing the disease, likely because people avoided using their water.”

Data indicate that the Legionnaires’ outbreak at a local hospital alone could not account for the increase in Legionnaires’ disease cases that occurred in Flint during the water crisis.

“Our study shows that during the water crisis, the risk of a Flint resident having Legionnaires’ disease increased as the amount of free chlorine in their water decreased,” said Shawn McElmurry, associate professor of civil and environmental engineering at Wayne State University and the FACHEP principal investigator. “Since municipalities typically evaluate the risk of waterborne illnesses by measuring free chlorine, a better understanding of how chlorine is deactivated can inform future water management policies and practices.”

Chlorine is a chemical that is routinely added to drinking water to kill microbes.
During the water crisis, the likelihood of Legionnaires’ disease occurring in communities adjacent to Flint also increased, probably due to the number of people who commuted into Flint.

The state has disputed the study, releasing the following statement:

The Michigan Department of Health and Human Services (MDHHS) recently learned that Wayne State University, the University of Michigan and Colorado State University will publish two journal articles based on data from the Flint Area Community Health and Environment Partnership (FACHEP) project.

Previously, FACHEP provided MDHHS with a draft of these journal articles which claim to explore the statistical relationship between the change in water source and the incidence of Legionnaire’s Disease in Flint and other Southeast Michigan counties and the prevalence of various strains of legionella found in the cities of Flint and Detroit.

MDHHS reviewed the draft articles as did an external, independent third party, KWR Watercycle Research Institute (KWR). KWR was asked to review the FACHEP project on behalf of the Michigan Department of Management and Budget. Both MDHHS and KWR found numerous flaws in the articles which were brought to FACHEP’s attention and appear to remain unaddressed. By publishing these inaccurate, incomplete studies at this point, FACHEP has done nothing to help the citizens of Flint and has only added to the public confusion on this issue.

The researchers not only failed to accurately describe conversations with MDHHS, but utilized variables in their dataset that inaccurately reflect the timing associated with cases of Legionnaires in Flint. Researchers also overestimate the risk to public health by focusing on a strain of the bacteria, serogroup 6, that is not typically associated with Legionnaires’ disease. FACHEP acknowledges that 16/18 of the environmental isolates that it found were serotype 6. Not a single case of serogroup 6 Legionnaire’s Disease was identified in Genesee county, despite widespread use of legionella cultures. As even FACHEP recognizes, more research is needed to evaluate the risk of this strain. Publishing this report now, however, implies that a public health risk exists when there may not be one.

In addition KWR noted that the report focusing on the link between the switch in the Flint water and increase in Legionnaires’ disease “…raises a number of serious critical questions with regard to the applied methodology, and gives little insight in the actual crude numbers in the various analyses.” KWR added that “[t]he paper is difficult to follow in places and does not provide insight into the crude data with which the statistical analyses were performed. The authors claim that their analyses reveal causal relations, but failed to distinguish between the demonstration of a statistical association, and its interpretation as a causal relation.”

Based upon concerns over FACHEP’s methodology, the State of Michigan informed FACHEP that it was only willing to continue the partnership under the independent review and oversight of KWR. FACHEP rejected the State’s offer to continue under these conditions.

Additional detail regarding the scientific concerns MDHHS has to these two journal articles can be found in “MDHHS Response to FACHEP Proceedings of the National Academy of Sciences Article” and “MDHHS Response to FACHEP American Society for Microbiology mBio Article” attachments.


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