Influenza Surveillance

2015 - 2016 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.
 

Report Activity Level
Week 20: May 15 - May 21, 2016 Sporadic
Week 19: May 6 - May 14, 2016 Sporadic
Week 18: May 1 - May 5, 2016 Sporadic
Week 17: April 24 - April 30, 2016 Sporadic
Week 16: April 17 - April 23, 2016 Sporadic
Week 15: April 10 - April 16, 2016 Localized
Week 14: April 3 - April 9, 2016 Localized
Week 13: March 27 - April 2, 2016 Localized
Week 12: March 20 - March 26, 2016 Regional
Week 11: March 13 - March 19, 2016 Regional
Week 10: March 6 - March 12, 2016 Regional
Week 9: February 27 - March 5, 2016 Regional
Week 8: February 21 - February 27, 2016 Regional
Week 7: February 14 - February 20, 2016 Localized
Week 6: February 7 - February 13, 2016 Regional
Week 5: January 31 - February 6, 2016 Localized
Week 4: January 24 - January 30, 2016 Localized
Week 3: January 17 - January 23, 2016 Localized
Week 2: January 10 - January 16, 2016 Sporadic
Week 1: January 3 - January 9, 2016 Sporadic
Week 52: December 27 - January 2, 2016 Sporadic
Week 51: December 20 - December 26, 2015 Sporadic
Week 50: December 13 - December 19, 2015 No Activity
Week 49: December 6 - December 12, 2015 Sporadic
Week 48: November 29 - December 5, 2015 Sporadic
Week 47: November 22 - November 28, 2015 Sporadic
Week 46: November 15 - November 21, 2015 Sporadic
Week 45: November 8 - November 14, 2015 Sporadic
Week 44: November 1 - November 7, 2015 Sporadic
Week 43: October 25 - October 31, 2015 No Activity
Week 42: October 18 - October 24, 2015 No Activity
Week 41: October 11 - October, 17, 2015 No Activity
Week 40: October 4 - October 10, 2015 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 ANDrecent 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.