Influenza Surveillance

2020 - 2021 Flu Activity Report

While influenza is not a reportable disease in Illinois, IDPH examines reports from many health care sites throughout the state. These sites include physician offices, emergency departments, and other clinics that report acute illness with influenza-like illness, and institutional settings such as nursing homes and prisons that report outbreaks. Accordingly, IDPH 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.

Week 1: January 3, 2021 - January 9, 2021
Week 53: December 27, 2020 - January 2, 2021
Week 52: December 20 - December 26, 2020
Week 51: December 13 - December 19, 2020
Week 50: December 6 - December 12, 2020
Week 49: November 29 - December 5, 2020
Week 48: November 22 - November 28, 2020
Week 47: November 15 - November 21, 2020
Week 46: November 8 - November 14, 2020
Week 45: November 1 - November 7, 2020
Week 44: October 25 - October 31, 2020
Week 43: October 18 - October 24, 2020
Week 42: October 11 - October 17, 2020
Week 41: October 4 - October 10, 2020
Week 40: September 27 - October 3, 2020

*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.