Sentinel Provider Surveillance: Influenza-like illness activity
Week 51 Activity (representing geographic distribution): Widespread
Week 51 ILI Activity (representing intensity of ILI activity): High
Provider offices across the US report the amount of influenza-like illness (ILI) they see in their patients each week during regular flu season. These outpatient providers’ offices, which include doctors’ offices, school health services, and community health centers, are called ‘sentinel sites.’ Here we present Massachusetts sentinel site data. Please note that the data do not represent only confirmed influenza cases, but also those just with ILI, which may be caused by other viruses. ILI is defined as fever above 100.01 in addition to either cough or sore throat. ILI is a marker of influenza and is used throughout the regular influenza season to monitor influenza since most people are not tested for influenza. Figure 1 shows that ILI activity continues to increase and is much higher than what is typically seen at this time of year. For more information, see CDC’s influenza surveillance website at www.cdc.gov/flu/weekly/fluactivitysurv.htm.
Figure 1: Percentage of ILI visits reported by sentinel provider sites
 CDC activity indicator also used in past seasons – indicates how widespread influenza activity level is in the state.
 New CDC activity indicator, introduced for 2010-2011 season – more quantitative indicator of the level of ILI activity across the state.