Introduction to Michigan Influenza Surveillance

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On October 4, 2012, the Michigan Department of Community Health confirmed the first cases of influenza identified by the state laboratory during the 2012-2013 Michigan flu season. Influenza A/H3, influenza A/H1N1 2009, and influenza B viruses were all identified. While two different types of influenza A viruses and influenza B viruses have now been confirmed in Michigan, it is too early to tell what influenza viruses will circulate during this influenza season or how severe the influenza season may be.

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

MDCH conducts year-round surveillance for influenza:

Each week during influenza season (October through May), MDCH 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.