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2010 - 2011 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
2011 May 15 May 21 No Activity
2011 May 8 May 14 No Activity
2011 May 1 May 7 No Activity
2011 April 24 April 30 Sporadic Activity
2011 April 17 April 23 Sporadic Activity
2011 April 10 April 16 Sporadic Activity
2011 April 3 April 9 Sporadic Activity
2011 March 27 April 2 Sporadic Activity
2011 March 20 March 26 Local Activity
2011 March 13 March 19 Local Activity
2011 March 6 March 12 Regional Activity
2011 February 27 March 5 Widespread Activity
2011 February 20 February 26 Widespread Activity
2011 February 13 February 19 Widespread Activity
2011 February 6 February 12 Widespread Activity
2011 January 30 February 5 Widespread Activity
2011 January 23 January 29 Widespread Activity
2011 January 16 January 22 Regional Activity
2011 January 9 January 15 Regional Activity
2011 January 2 January 8 Regional Activity
2010 December 26 January 1 Regional Activity
2010 December 19 December 25 Local Activity
2010 December 12 December 18 Local Activity
2010 December 5 December 11 Local Activity
2010 November 28 December 4 Local Activity
2010 November 21 November 27 Sporadic Activity
2010 November 14 November 20 Sporadic Activity
2010 November 7 November 13 Sporadic Activity
2010 October 31 November 6 Sporadic Activity
2010 October 24 October 30 Sporadic Activity
2010 October 17 October 23 Sporadic Activity
2010 October 10 October 16 No Activity
2010 October 3 October 9 Sporadic 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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