Weekly U.S. Influenza Surveillance Report

Updated September 30, 2022

FluView a weekly influenza surveillance report prepared by the Influenza Division
2021-2022 Influenza Season for Week 38, ending September 24, 2022

All data 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 are 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 38 Data Cumulative since
October 3, 2021
(Week 40)
No. of specimens tested 50,292 3,743,239
No. of positive specimens (%) 677 (1.3%) 136,829 (3.7%)
Positive specimens by type
Influenza A 628 (92.8%) 134,464 (98.3%)
Influenza B 49 (7.2%) 2,365 (1.7%)

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 subtype/lineage. Data from public health laboratories are used to monitor the proportion of circulating viruses that belong to each influenza 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 38 Data Cumulative since
October 3, 2021
(Week 40)
No. of specimens tested 9,907 1,115,302
No. of positive specimens 52 26,181
Positive specimens by type/subtype    
         Influenza A 47 (90.4%) 26,020 (99.4%)
            (H1N1)pdm09 12 (36.4%) 75 (0.4%)
             H3N2 21 (63.6%) 20,591 (99.6%)
             H3N2v 0 4 (<0.1%)
             Subtyping not performed 14 5,350
        Influenza B 5 (9.6%) 161 (0.6%)
            Yamagata lineage 0 1 (2.3%)
            Victoria lineage 0 43 (97.7%)
            Lineage not performed 5 117

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 influenza-like illness [ILI (fever plus cough or sore throat)], not laboratory-confirmed influenza, and will therefore capture respiratory illness visits due to infection with any pathogen that can present with similar symptoms, including influenza, SARS-CoV-2, and RSV. Due to the COVID-19 pandemic, health care-seeking behaviors have changed, and people may be accessing the health care system in alternative settings not captured as a part of ILINet or at a different point in their illness than they might have before the pandemic. 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. CDC is tracking the COVID-19 pandemic in a weekly publication called COVID Data Tracker Weekly Review. Information about other respiratory virus activity can be found on CDC’s National Respiratory and Enteric Virus Surveillance System (NREVSS) website.

Outpatient Respiratory Illness Visits

Nationwide during week 38, 2.2% 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 38, the percentage of visits for respiratory illness reported in ILINet was 9.0% among those 0-4 years, 3.5% among those 5-24 years, 1.1% among those 25-49 years, 0.7% among those 50-64 years, and 0.6% among those 65 years and older.

national levels of ILI and ARI by age group

* 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 | View Full Screen

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 38

(Week ending
Sep. 24, 2022)

Week 37

(Week ending 
Sep. 17, 2022)

Week 38

(Week ending
Sep. 24, 2022)

Week 37

(Week ending
Sep. 17, 2022)

Very High 0 0 4 3
High 3 2 13 8
Moderate 2 2 29 24
Low 9 5 85 73
Minimal 40 46 520 555
Insufficient Data 1 0 278 266

 

*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

Long-term Care Facility (LTCF) Surveillance

LTCFs (e.g., nursing homes/skilled nursing, long-term care for the developmentally disabled, and assisted living facilities) from all 50 states and U.S. territories report data on influenza virus infections among residents through the National Healthcare Safety Network (NHSN) Long-term Care Facility Component. During week 38, 31 (0.2%) of 14,528 reporting LTCFs reported at least one influenza positive test among their residents.


Additional information about long-term care facility surveillance:
Surveillance Methods | Additional Data

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 14 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 June 11, 2022, will not be included in FluSurv-NET for the 2021-2022 season. Data on patients admitted through June 11, 2022, will continue to be updated 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

HHS Protect Hospitalization Surveillance

Hospitals report to HHS Protect the number of patients admitted with laboratory-confirmed influenza. During week 38, 739 patients with laboratory-confirmed influenza were admitted to the 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 29, 2022, 8.7% of the deaths that occurred during the week ending September 24, 2022 (week 38), were due to pneumonia, influenza, and/or COVID-19 (PIC). This percentage is above the epidemic threshold of 5.6% for this week. Among the 2,035 PIC deaths reported for this week, 1,014 had COVID-19 listed as an underlying or contributing cause of death on the death certificate, and six listed influenza, indicating that current PIC mortality is due primarily to COVID-19 and not 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 in weeks 30 (the week ending July 30, 2022) and 33 (the week ending August 20, 2022) of the 2021-2022 season were reported to CDC during week 38. Both deaths were associated with influenza A viruses for which no subtyping was performed.

A total of 39 influenza-associated pediatric deaths occurring during the 2021-2022 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.