Shawn McElmurray, Ph.D.
Wayne State University
NIEHS grantees and colleagues found that an estimated 80 percent of Legionnaires’ disease cases that occurred during an outbreak in Genesee County, Michigan, could be attributed to the city of Flint’s drinking water supply being changed to the Flint River.
The researchers conducted a detailed statistical analysis of data on Legionnaires’ cases in the Michigan counties of Genesee, Wayne, and Oakland from 2011 to 2016. They determined that in 2014 and 2015, there was an increase in the risk of acquiring Legionnaires’ disease across the Flint water distribution system that was consistent with a system-wide proliferation of Legionella pneumophila bacteria. Based on their calculations, the researchers attributed an estimated 80 percent of Legionnaires’ cases during this period to the change in the water supply.
They found that the risk of a Flint resident having Legionnaires’ disease increased as the amount of free chlorine in their water decreased. The analysis also suggested that the 0.2 or 0.5 parts per million chlorine residual levels recommended by regulatory agencies might not be sufficient to protect communities from L. pneumophila exposure when water quality conditions support strong growth of the bacteria, which was the case in Flint during and immediately after the water change.
Citation: Zahran S, McElmurry SP, Kilgore PE, Mushinski D, Press J, Love NG, Sadler RC, Swanson MS. 2018. Assessment of the Legionnaires' disease outbreak in Flint, Michigan. Proc Natl Acad Sci U S A 115(8):E1730–E1739.