FluView Summary ending on September 2, 2023

Updated September 8, 2023

FluView a weekly influenza surveillance report prepared by the Influenza Division

 

2022-2023 Influenza Season

Week 35 ending September 2, 2023

 All data in this report are preliminary and may change as more reports are received.

 A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component, is available on the surveillance methods page.

 Additional information on the current and previous influenza seasons for each surveillance component is available on FluView Interactive.

U.S. Virologic Surveillance

Clinical Laboratories

The results of tests performed by clinical laboratories nationwide are summarized below. Data from clinical laboratories (the percentage of specimens tested that are positive for influenza) are used to monitor whether influenza activity is increasing or decreasing.

 

results of tests from Clinical Laboratories
Week 35
Data Cumulative since October 2, 2022(Week 40)
No. of specimens tested 30,867 3,965,616
No. of positive specimens (%) 233 (0.8%) 358,391 (9.0%)
Positive specimens by type
Influenza A 155 (66.5%) 348,771 (97.3%)
Influenza B 78 (33.5%) 9,620 (2.7%)

Public Health Laboratories

The results of tests performed by public health laboratories nationwide are summarized below.  Data from public health laboratories are used to monitor the proportion of circulating viruses that belong to each influenza virus type/subtype/lineage. Viruses known to be associated with recent live attenuated influenza vaccine (LAIV) receipt or found upon further testing to be a vaccine virus are not included as they are not circulating influenza viruses.

results of tests from Public Health Laboratories
Week 35 Data Cumulative since
October 2, 2022
(Week 40)
No. of specimens tested 1,466 281,013
No. of positive specimens 41 30,893
Positive specimens by type/subtype    
         Influenza A 35 (85.4%) 29,484 (95.4%)
            (H1N1)pdm09 20 (87.0%) 7,420 (29.6%)
             H3N2 3 (13.0%) 17,683 (70.4%)
             H3N2v 0 2 (<0.1%)
             Subtyping not performed 12 4,379
        Influenza B 6 (14.6%) 1,409 (4.6%)
            Yamagata lineage 0 (0%) 0
            Victoria lineage 4 (100%) 1,147 (100%)
            Lineage not performed 2 262

Additional virologic surveillance information for current and past seasons:
Surveillance Methods | FluView Interactive: National, Regional, and State Data or Age Data

Outpatient Respiratory Illness Surveillance

The U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) monitors outpatient visits for respiratory illness referred to as influenza-like illness [ILI (fever plus cough or sore throat)], not laboratory-confirmed influenza, and may capture respiratory illness visits due to infection with any pathogen that can present with similar symptoms, including influenza, SARS-CoV-2, and RSV. Therefore, it is important to evaluate syndromic surveillance data, including that from ILINet, in the context of other sources of surveillance data to obtain a complete and accurate picture of influenza, SARS-CoV-2, and other respiratory virus activity. Other respiratory virus surveillance data can be found on CDC’s COVID Data Tracker, NCIRD Surveillance Systems website and National Respiratory and Enteric Virus Surveillance System (NREVSS) website.

Outpatient Respiratory Illness Visits

Nationwide during week 35 1.8% of patient visits reported through ILINet were due to respiratory illness that included fever plus a cough or sore throat, also referred to as ILI. Multiple respiratory viruses are co-circulating, and the relative contribution of influenza virus infection to ILI varies by location.

national levels of ILI and ARI

* Effective October 3, 2021 (week 40), the ILI definition (fever plus cough or sore throat) no longer includes “without a known cause other than influenza.”

View Chart Data (current season only) | View Full Screen

Outpatient Respiratory Illness Visits by Age Group

More than 70% of ILINet participants provide both the number of patient visits for respiratory illness and the total number of patient visits for the week broken out by age group. Data from this subset of providers are used to calculate the percentages of patient visits for respiratory illness by age group.

During week 35, the percentage of visits for respiratory illness reported in ILINet was 6.2% among those 0-4 years, 3.1% among those 5-24 years, 1.6% among those 25-49 years, 1.1% among those 50-64 years, and 0.8% among those 65 years and older.

Outpatient Respiratory Illness Activity Map

Data collected in ILINet are used to produce a measure of ILI activity* by state/jurisdiction and Core Based Statistical Areas (CBSA).

ILI Activity by State/Jurisdiction and Core Based Statistical Area
Activity Level Number of Jurisdictions Number of CBSAs
Week 35

(Week ending
Sept. 2, 2023)

Week 34

(Week ending 
Aug. 26, 2023)

Week 35

(Week ending
Sept. 2, 2023)

Week 34

(Week ending
Aug. 26, 2023)

Very High 0 0 2 2
High 0 0 13 15
Moderate 1 1 32 26
Low 8 7 57 55
Minimal 45 46 562 562
Insufficient Data 1 1 263 269

 

*Data collected in ILINet may disproportionally represent certain populations within a jurisdiction or CBSA, and therefore, may not accurately depict the full picture of influenza activity for the entire jurisdiction or CBSA. Differences in the data presented here by CDC and independently by some health departments likely represent differing levels of data completeness with data presented by the health department likely being the more complete.


Additional information about medically attended visits for ILI for current and past seasons:
Surveillance Methods | FluView Interactive: National, Regional, and State Data or ILI Activity Map

Hospitalization Surveillance

FluSurv-NET

The Influenza Hospitalization Surveillance Network (FluSurv-NET) conducts population-based surveillance for laboratory-confirmed influenza-related hospitalizations in select counties in 13 states and represents approximately 9% of the U.S. population. FluSurv-NET hospitalization data are preliminary. Patients admitted for laboratory-confirmed influenza-related hospitalization after April 30, 2023, will not be included in FluSurv-NET for the 2022-2023 season. Data on patients admitted through April 30, 2023, will continue to be updated on FluView Interactive as additional information is received.


Additional FluSurv-NET hospitalization surveillance information for current and past seasons and additional age groups:
Surveillance Methods |FluView Interactive: Rates by Age, Sex, and Race/Ethnicity or Data on Patient Characteristics | RESP-NET Interactive

HHS Protect Hospitalization Surveillance

Hospitals report to HHS Protect the number of patients admitted with laboratory-confirmed influenza. During week 35, 823 patients with laboratory-confirmed influenza were admitted to a hospital.


Additional HHS Protect hospitalization surveillance information:
Surveillance MethodsAdditional Data

Mortality Surveillance

National Center for Health Statistics (NCHS) Mortality Surveillance

Based on NCHS mortality surveillance data available on September 7, 2023, 6.8% of the deaths that occurred during the week ending September 2, 2023 (week 35), were due to pneumonia, influenza, and/or COVID-19 (PIC). This percentage is above the epidemic threshold of 5.5% for this week. Among the 1,160 PIC deaths reported for this week, 352 had COVID-19 listed as an underlying or contributing cause of death on the death certificate, and 4 listed influenza. The data presented are preliminary and may change as more data are received and processed.


Additional pneumonia, influenza and COVID-19 mortality surveillance information for current and past seasons:
Surveillance Methods | FluView Interactive

Influenza-Associated Pediatric Mortality

Two influenza-associated pediatric deaths occurring during the 2022-2023 season were reported to CDC during week 35. One death was associated with an influenza A(H3) virus and occurred during week 46 of 2022 (the week ending November 19, 2022). The other death was associated with an influenza A virus for which no subtyping was performed and occurred during week 4 of 2023 (the week ending January 28, 2023).

A total of 174 influenza-associated pediatric deaths occurring during the 2022-2023 season have been reported to CDC.


Additional pediatric mortality surveillance information for current and past seasons:
Surveillance Methods | FluView Interactive

Additional National and International Influenza Surveillance Information

FluView Interactive: FluView includes enhanced web-based interactive applications that can provide dynamic visuals of the influenza data collected and analyzed by CDC. These FluView Interactive applications allow people to create customized, visual interpretations of influenza data, as well as make comparisons across flu seasons, regions, age groups and a variety of other demographics.

National Institute for Occupational Safety and Health: Monthly surveillance data on the prevalence of health-related workplace absenteeism among full-time workers in the United States are available from NIOSH.

U.S. State and local influenza surveillance: Select a jurisdiction below to access the latest local influenza information.

World Health Organization:
Additional influenza surveillance information from participating WHO member nations is available through
FluNet and the Global Epidemiology Reports.

WHO Collaborating Centers for Influenza:
Australia, China, Japan, the United Kingdom, and the United States (CDC in Atlanta, Georgia)

Europe:
The most up-to-date influenza information from Europe is available from WHO/Europe and the European Centre for Disease Prevention and Control.

Public Health Agency of Canada:
The most up-to-date influenza information from Canada is available in Canada’s weekly FluWatch report.

Public Health England:
The most up-to-date influenza information from the United Kingdom is available from Public Health England.

Any links provided to non-Federal organizations are provided solely as a service to our users. These links do not constitute an endorsement of these organizations or their programs by CDC or the Federal Government, and none should be inferred. CDC is not responsible for the content of the individual organization web pages found at these links.

A description of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component is available on the surveillance methods page.