Week Ending March 2nd, 2024 (Week 9)

Overview

• Influenza-like illness (ILI)¹ activity in Kane County is estimated to be MODERATE².

• 5.77% of all visits at Kane County emergency departments were for influenza-like illness.³

• 1 influenza-related ICU admission was reported to the health department; there have been 41 total for the season.

• No pediatric deaths due to influenza were reported.

• To date, 2 outbreaks of influenza have been reported in long-term care/assisted living facilities in Kane County.

• 138 of 950 (14.5%) specimens tested for influenza were positive at 4 reporting labs.⁴

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• 0.41% of students were absent from school due to ILI.

Emergency Department Visits

5.77% of hospital emergency department visits were for influenza-like illness.

Each week, data for the 2023-24 season will be presented with data from previous flu seasons to show the trend of ED visits for ILI over time.

The baseline for ILI related emergency department visits in Kane County is 3.75% of all emergency department visits.⁵

Emergency department visits for ILI in Kane County had the following age distribution:

• 0-4 years: 14.9%
• 5-24 years: 42.0%
• 25-49 years: 23.1%
• 50-64 years: 7.1%
• 65+ years: 12.9%

Laboratory Tests

Student Absenteeism

0.41% of students were absent from school due to ILI.

The Kane County Health Department received absenteeism reports from 105 of 170 (61.8%) public schools.

There were no reported clusters or increased ILI absences in schools.

*School Absenteeism from March 2020 through May 2022 is not reported due to COVID-19

National Snapshot^6

• The activity levels compare the mean reported percent of visits due to ILI during the current week to the mean reported percent of visits due to ILI during non-influenza weeks. The 13 activity levels correspond to the number of standard deviations below, at, or above the mean for the current week compared with the mean during non-influenza weeks. 

• This map uses the proportion of outpatient visits to healthcare providers for influenza-like illness to measure the ILI activity level within a state. It does not, however, measure the extent of geographic spread of flu within a state. Therefore, outbreaks occurring in a single city could cause the state to display high activity levels.

• Data collected in ILINet may disproportionately represent certain populations within a state, and therefore may not accurately depict the full picture of influenza activity for the whole state.

¹Influenza-like illness (ILI) is defined as fever ≥ 100°F with a cough and/or sore throat.

²ILI Activity is defined by: Low (0-3 standard deviations above ED mean), Moderate (4-7 standard deviations above ED mean), and High (8+ standard deviations above ED mean).

³The Kane County Health Department tracks seasonal influenza absenteeism and laboratory testing through ILI surveillance reporting. Emergency department visits related to ILI are automatically tracked through the Electronic Surveillance System for the Early Notification of Community-based Epidemics (ESSENCE). ED visits of interest were identified using the ILI chief complaint and discharge diagnosis query definition.

⁴Rapid influenza testing cannot distinguish influenza infections caused by novel influenza A viruses. The sensitivity of this type of testing has been shown to range between 20-100% for seasonal influenza viruses. A negative result does not exclude influenza virus infection.

⁵Baseline for Emergency Department (ED) related visits was calculated using the mean percentage of visits and adding two standard deviations from 2017-18, 2018-19, select weeks in 2019-2020, 2021-22, and 2022-23 influenza season data for non-influenza weeks. Non-influenza weeks are defined as two or more consecutive weeks when each week accounts for less than 2% of the season’s total positive influenza specimens in Kane County labs.

⁶The National Snapshot comes directly from the FluView interactive portal prepared by the CDC Influenza Division using ILINet data. FluView can be accessed at https://gis.cdc.gov/grasp/fluview/main.html.

*All data in this report are provisional.

The Kane County Health Department thanks all surveillance partners for assisting with collecting and sharing this information. 

Additional Resources

All weekly reports are available online at https://kanehealth.com/Pages/Providers-Flu.aspx.

CDC flu information can be found at https://www.cdc.gov/flu/index.htm and https://www.cdc.gov/flu/professionals/index.htm.

National flu surveillance: https://www.cdc.gov/flu/weekly/index.htm.

IDPH flu surveillance: https://dph.illinois.gov/topics-services/diseases-and-conditions/influenza/influenza-surveillance/report.html.

For additional information on ILI surveillance, please contact the Kane County Health Department epidemiology team at kchdepi@kanecountyil.gov.