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2004 - 2005 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.

Year Week Beginning Week Ending Reported Influenza Activity
2005 April 24 April 30 No Activity
2005 April 17 April 23 No Activity
2005 April 10 April 16 Sporadic Activity
2005 April 3 April 9 Sporadic Activity
2005 March 27 April 2 Sporadic Activity
2005 March 20 March 26 Sporadic Activity
2005 March 13 March 19 Local Activity
2005 March 6 March 12 Local Activity
2005 February 27 March 5 Regional Activity
2005 February 20 February 26 Regional Activity
2005 February 13 February 19 Regional Activity
2005 February 6 February 12 Regional Activity
2005 January 30 February 5 Regional Activity
2005 January 23 January 29 Regional Activity
2005 January 16 January 22 Local Activity
2005 January 9 January 15 Local Activity
2005 January 2 January 8 Local Activity
2005 December 26 January 1 Sporadic Activity
2004 December 19 December 25 Sporadic Activity
2004 December 12 December 18 Sporadic Activity
2004 December 5 December 11 Sporadic Activity
2004 November 28 December 4 Sporadic Activity
2004 November 21 November 27 Sporadic Activity
2004 November 14 November 20 Sporadic Activity
2004 November 7 November 13 Sporadic Activity
2004 October 31 November 6 No Activity
2004 October 24 October 30 No Activity
2004 October 17 October 23 No Activity
2004 October 10 October 16 No Activity
2004 October 3 October 9 No Activity
2004 September 26 October 2 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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