Introduction to Michigan Influenza Surveillance

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The Michigan Department of Health and Human Services (MDHHS) determines influenza activity based on many sources of information including data from the MDHHS laboratory, Influenza Sentinel Physicians, sentinel laboratories, sentinel hospitals, the Michigan Disease Surveillance System (MDSS), and MDHHS syndromic surveillance. 

MDHHS conducts year-round surveillance for influenza:

Each week during influenza season (October through May), MDHHS reports the estimated level of influenza activity in the state to the Centers for Disease Control and Prevention (CDC).  The five levels, from lowest to highest, are: 

  • No activity: No laboratory-confirmed cases of influenza and no reported increase in the number of cases of influenza-like illness (ILI) 
  • Sporadic: Isolated laboratory-confirmed influenza cases or a single influenza outbreak has been reported, but no increase in ILI activity 
  • Local: Outbreaks of Influenza or increases in ILI cases and recent laboratory-confirmed influenza in a single region of the state. 
  • Regional: Outbreaks of influenza or increases in ILI and recent laboratory confirmed Influenza in at least 2 regions of the state. 
  • Widespread: Outbreaks of influenza or increases in ILI cases cases and recent laboratory-confirmed influenza in over half the regions of the state.

A map of the State and Territorial Epidemiologists' Reports from Michigan and throughout the U.S. can be viewed on the CDC influenza website from October through May.