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2011 - 2012 Flu Activity Report

While influenza is not a reportable disease in Illinois, the Illinois Department of Public Health examines reports from many health care sites throughout the state. These sites include physician offices, emergency departments and nursing homes that report acute illness, and schools that report absenteeism rates. Accordingly, the Department monitors disease trends and influenza activities as they occur on a weekly basis.

A detailed surveillance report for each week can be viewed by clicking on the desired week in the table below. This weekly surveillance report summarizes regional and state influenza data used to determine the weekly influenza activity level and national activity levels reported by state and territorial epidemiologists.

Year Week Beginning Week Ending Reported Influenza Activity
2012 May 13 May 19 No Activity
2012 May 6 May 12 Sporadic Activity
2012 April 29 May 5 Sporadic Activity
2012 April 22 April 28 Sporadic Activity
2012 April 15 April 21 Sporadic Activity
2012 April 8 April 14 Sporadic Activity
2012 April 1 April 7 Sporadic Activity
2012 March 25 March 31 Regional Activity
2012 March 18 March 24 Regional Activity
2012 March 11 March 17 Widespread Activity
2012 March 4 March 10 Widespread Activity
2012 February 26 March 3 Widespread Activity
2012 February 19 February 25 Widespread Activity
2012 February 12 February 18 Regional Activity
2012 February 5 February 11 Regional Activity
2012 January 29 February 4 Regional Activity
2012 January 22 January 28 Sporadic Activity
2012 January 15 January 21 Sporadic Activity
2012 January 8 January 14 Sporadic Activity
2012 January 1 January 7 Sporadic Activity
2011 December 25 December 31 Sporadic Activity
2011 December 18 December 24 No Activity
2011 December 11 December 17 No Activity
2011 December 4 December 10 No Activity
2011 November 27 December 3 No Activity
2011 November 20 November 26 Sporadic Activity
2011 November 13 November 19 Sporadic Activity
2011 November 6 November 12 No Activity
2011 October 30 November 5 No Activity
2011 October 23 October 29 No Activity
2011 October 16 October 22 No Activity
2011 October 9 October 15 No Activity
2011 October 2 October 8 No Activity

No Activity No lab confirmed cases †
Sporadic Activity Isolated lab-confirmed cases OR Lab confirmed outbreak in one institution ‡
Local Activity Recent (within the past 3 weeks) lab evidence of influenza in region with increased ILI* OR Recent (within the past 3 weeks) lab evidence of influenza in region with the outbreaks; virus activity is no greater than sporadic in other regions**
Regional Activity Increased ILI* in >2 but less than half of the regions AND recent (within the past 3 weeks) lab confirmed influenza in the affected regions. OR Institutional outbreaks (ILI or lab confirmed) in >2 and less than half of the regions AND recent lab confirmed influenza in the affected regions**. A region is defined as the regions States use for public health purposes.
Widespread Activity Increased ILI* and/or institutional outbreaks (ILI* or lab confirmed) in at least half of the regions** AND recent (within the past 3 weeks) lab confirmed influenza in the state.

*ILI activity can be assessed using a variety of data sources including sentinel providers, school/workplace absenteeism, and other syndromic surveillance systems that monitor influenza-like illness.
Lab confirmed case=case confirmed by rapid diagnostic test, antigen detection, culture, or PCR. Care should be given when relying on results of point of care rapid diagnostic test kits during times when influenza is not circulating widely. The sensitivity and specificity of these tests vary and the predicative value positive may be low outside the time of peak influenza activity. Therefore, a state may wish to obtain laboratory confirmation of influenza by testing methods other than point of care rapid tests for reporting the first laboratory confirmed case of influenza of the season.
Institution includes nursing home, hospital, prison, school, etc.
** Region: population under surveillance in a defined geographical subdivision of a state. A region could be comprised of 1 or more counties and would be based on each state's specific circumstances. Depending on the size of the state, the number of regions could range from 2 to approximately 12. The definition of regions would be left to the state but existing state health districts could be used in many states. Allowing states to define regions would avoid somewhat arbitrary county lines and allow states to make divisions that make sense based on geographic population clusters. Focusing on regions larger than counties would also improve the likelihood that data needed for estimating activity would be available.

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535 West Jefferson Street • Springfield, Illinois 62761 • Phone 217-782-4977 • Fax 217-782-3987 • TTY 800-547-0466
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