MDHHS completes Genesee County Legionnaires' Disease case review, finds only one common source


CONTACT: Angela Minicuci, (517) 241-2112

LANSING, Mich. – The Michigan Department of Health and Human Services (MDHHS) committed to further reviewing the Genesee County Legionnaires’ Disease cases during 2014 and 2015. As a result of that review, MDHHS has compiled a chart book which breaks down the cases by timeline, geography, potential sources, and baseline data.

In 2014 and 2015, a total of 90 cases of Legionnaires’ Disease were reported to the Genesee County Health Department (GCHD). In response, GCHD began investigating cases by conducting interviews and reviewing medical records. Interviews are standard practice for case investigations and are conducted to gather information about disease onset and potential sources of exposure to Legionella. Information about symptom onset, patient residence, recent healthcare received, recent travel and other variables are collected.

Nationwide, the rate of Legionnaires’ Disease cases has increased substantially in recent years, by 286 percent during 2000–2014. Similarly, Michigan experienced a 375 percent increase in the rate between 2000 and 2016, or about a 13 percent annual increase (Michigan has more recent data available than national data). Michigan’s highest incidence rate occurred in 2013 (2.75 cases per 100,000 population), with second highest rate in 2016 (2.71 per 100,000 population).

There were two waves of illness evident in 2014 and 2015, with a return to expected levels during the spring months of 2015, as well as expected baseline levels in 2016 and 2017.  The MDHHS review of the 2014-2015 Genesee County cases found:

  • Geographically, the cases were distributed throughout Genesee County.
    • The percentage of cases living on the Flint water system was nearly identical in 2014-2015 period and the 2011-2013 period.
    • During 2014-2015, the majority of Legionnaires’ Disease cases (68 percent) lived in a residence that was not serviced by City of Flint water system.
    • Similarly, in the baseline period (2011-2013), 64 percent of cases lived in a residence that was not serviced by City of Flint water system during their incubation period.
  • Only one common source has been identified that explains the majority of the increase in cases – a common health facility exposure at McLaren Flint Hospital.
    • No other large building with high risk plumbing was identified as a common source of exposure.
    • Of the 83 patients for whom a complete exposure history was available, 54 (65 percent) case patients had hospital building exposure.
    • 51 of 54 (94 percent) case patients with hospital healthcare exposures were at McLaren Flint Hospital.
      • 46 of 54 case patients (85 percent) were exposed only to McLaren Flint.
    • Of the 32 cases who did not have a McLaren Flint health-care associated exposure, only nine lived on Flint water.
    • After removing the cases with known McLaren Flint exposure, the number of Legionnaires’ Disease cases during 2014-2015 was higher for people not living on the Flint water system than for people living on the system.
    • MDHHS has found no demonstrated clustering of non-healthcare related cases in patients with residences serviced by the Flint water system.
      • No cases on the Flint water system occurred after the week of August 15, 2015, after McLaren Flint Hospital superheated their water system and installed secondary treatment systems.

For any resident that develops pneumonia symptoms, it’s recommended that you see a doctor right away. Signs and symptoms of pneumonia can include cough, shortness of breath, muscle aches, headache, and high fever. Be sure to tell the doctor if you have used a hot tub, spent any nights away from home, or stayed in a hospital in the last two weeks.

For the full Chart Book and to review the case breakdowns, visit the MDHHS website.

# # #