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Weekly U.S. Influenza Surveillance Report

FluView: A Weekly Influenza Surveillance Report Prepared by the Influenza Division

2017-2018 Influenza Season Week 19 ending May 12, 2018


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

Synopsis:

During week 19 (May 6-12, 2018), influenza activity continued to decrease in the United States.

  • Viral Surveillance:Overall, influenza A(H3) viruses have predominated this season. Since early March, influenza B viruses have been more frequently reported than influenza A viruses. The percentage of respiratory specimens testing positive for influenza in clinical laboratories decreased.
  • Pneumonia and Influenza Mortality: The proportion of deaths attributed to pneumonia and influenza (P&I) was below the system-specific epidemic threshold in the National Center for Health Statistics (NCHS) Mortality Surveillance System.
  • Influenza-associated Pediatric Deaths: Three influenza-associated pediatric deaths were reported.
  • Influenza-associated Hospitalizations: A cumulative rate of 106.6 laboratory-confirmed influenza-associated hospitalizations per 100,000 population was reported.
  • Outpatient Illness Surveillance: The proportion of outpatient visits for influenza-like illness (ILI) was 1.2%, which is below the national baseline of 2.2%. All 10 regions reported ILI below region-specific baseline levels. New York City, the District of Columbia, Puerto Rico and all 50 states experienced minimal ILI activity.
  • Geographic Spread of Influenza: The geographic spread of influenza in two states was reported as widespread; Guam, Puerto Rico and three states reported regional activity; nine states reported local activity; the District of Columbia, the U.S. Virgin Islands and 33 states reported sporadic activity; and three states reported no influenza activity.

National and Regional Summary of Select Surveillance Components

HHS Surveillance Regions* Data for current week Data cumulative since October 1, 2017 (week 40)
Out-patient ILI Number of jurisdictions reporting regional or widespread activity§ % respiratory specimens positive for flu in clinical laboratories A(H1N1)pdm09 A (H3) A (Subtyping not Performed)
B Victoria lineage B Yamagata lineage B lineage not performed Pediatric Deaths
Influenza test results from public health laboratories only
Nation Normal 7 of 54 3.9% 5,634 31,795 619 1,316 10,381 3,592 168
Region 1 Normal 3 of 6 7.5% 317 1,824 5 84 573 62 5
Region 2 Normal 2 of 4 6.7% 314 2,032 22 40 448 383 9
Region 3 Normal 0 of 6 7.7% 1,096 3,747 14 331 1,579 141 16
Region 4 Normal 1 of 8 5.4% 928 2,938 102 50 787 637 42
Region 5 Normal 0 of 6 10.3% 804 6,622 90 89 1,922 226 31
Region 6 Normal 0 of 5 1.7% 358 1,318 8 49 515 326 29
Region 7 Normal 0 of 4 3.6% 132 1,340 9 10 613 34 4
Region 8 Normal 0 of 6 4.7% 330 2,687 22 159 1,027 81 5
Region 9 Normal 1 of 5 2.6% 881 7,765 336 491 2,349 928 22
Region 10 Normal 0 of 4 6.9% 474 1,521 11 13 568 774 5

*https://www.hhs.gov/about/agencies/iea/regional-offices/index.html
† Elevated means the % of visits for ILI is at or above the national or region-specific baseline
§ Includes all 50 states, the District of Columbia, Guam, Puerto Rico, and U.S. Virgin Islands
‡ National data are for current week; regional data are for the most recent three weeks


U.S. Virologic Surveillance:

WHO and NREVSS collaborating laboratories, which include both public health and clinical laboratories located in all 50 states, Puerto Rico, and the District of Columbia, report to CDC the total number of respiratory specimens tested for influenza and the number positive for influenza by virus type. In addition, public health laboratories also report the influenza A subtype (H1 or H3) and influenza B lineage information of the viruses they test and the age or age group of the persons from whom the specimens were collected.

Additional virologic data, including national, regional and select state-level data, can be found at: http://gis.cdc.gov/grasp/fluview/fluportaldashboard.html. Age group proportions and totals by influenza subtype reported by public health laboratories can be found at: http://gis.cdc.gov/grasp/fluview/flu_by_age_virus.html.

The results of tests performed by clinical laboratories are summarized below.

  Week 19 Data Cumulative since
October 1, 2017 (Week 40)
No. of specimens tested 9,341 1,191,471
No. of positive specimens (%) 363 (3.9%) 222,966 (18.7%)
Positive specimens by type    
    Influenza A 107 (29.5%) 150,744 (67.6%)
    Influenza B 256 (70.5%) 72,222 (32.4%)
INFLUENZA Virus Isolated
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The results of tests performed by public health laboratories, as well as the age group distribution of influenza positive tests, during the current week are summarized below.

  Week 19 Data Cumulative since
October 1, 2017 (Week 40)
No. of specimens tested 268 97,194
No. of positive specimens* 48 53,337
Positive specimens by type/subtype    
    Influenza A 13 (27.1%) 38,048 (71.3%)
    A(H1N1)pdm09 6 (46.2%) 5,634 (14.8%)
    H3N2 6 (46.2%) 31,795 (83.6%)
    Subtyping not performed 1 (7.7%) 619 (1.6%)
    Influenza B 35 (72.9%) 15,289 (28.7%)
     Yamagata lineage 27 (77.1%) 10,381 (67.9%)
     Victoria lineage 0 (0%) 1,316 (8.6%)
      Lineage not performed 8 (22.9%) 3,592 (23.5%)

*The percent of specimens testing positive for influenza is not reported because public health laboratories often receive samples that have already tested positive for influenza at a clinical laboratory and therefore percent positive would not be a valid indicator of influenza activity. Additional information is available at http://www.cdc.gov/flu/weekly/overview.htm.

INFLUENZA Virus Isolated
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INFLUENZA Virus Isolated
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Influenza Virus Characterization:

Close monitoring of influenza viruses is required to better assess the potential impact on public health. CDC characterizes influenza viruses through one or more tests including genomic sequencing and hemagglutination inhibition (HI) (i.e., hemagglutination inhibition (HI) and/or neutralization assays). These data are used to monitor for changes in circulating influenza viruses and to compare how similar currently circulating influenza viruses are to the reference viruses used for developing influenza vaccines. Antigenic and genetic characterization of circulating influenza viruses can give an indication of the influenza vaccine's ability to produce an immune response against the wide array of influenza viruses co-circulating, but annual vaccine effectiveness estimates are needed to determine how much protection has been provided to the population by vaccination. On February 15, 2018, interim influenza vaccine effectiveness estimates for the 2017-2018 season were released and are available here.

For nearly all influenza-positive surveillance samples received at CDC, next-generation sequencing is performed to determine the genetic identity of circulating influenza viruses and to monitor viruses for evidence of genetic changes. Viruses are classified into genetic clades/subclades based on analysis of the genetic sequences of the HA gene segments. However, genetic changes do not always result in antigenic change. Extensive genetic variation may exist in circulating viruses, with no evidence of substantial antigenic drift. Antigenic drift is evaluated by comparing cell-propagated circulating viruses with cell-propagated reference viruses representing currently recommended vaccine components.

CDC has antigenically or genetically characterized 3,174 influenza viruses collected during October 1, 2017 – May 12, 2018, and submitted by U.S. laboratories, including 791 influenza A(H1N1)pdm09 viruses, 1,274 influenza A(H3N2) viruses, and 1,109 influenza B viruses.

    Influenza A Viruses

    • A (H1N1)pdm09: Phylogenetic analysis of the HA genes from 791 A(H1N1)pdm09 viruses showed that all belonged to clade 6B.1. Seven hundred and eight A(H1N1)pdm09 viruses were antigenically characterized, and all were antigenically similar (analyzed using HI with ferret antisera) to the reference 6B.1 virus A/Michigan/45/2015, representing the recommended influenza A(H1N1)pdm09 reference virus for the 2017–18 Northern Hemisphere influenza vaccines.
    • A (H3N2): Phylogenetic analysis of the HA genes from 1,274 A(H3N2) viruses revealed extensive genetic diversity with multiple clades/subclades co-circulating. The HA genes of circulating viruses belonged to clade 3C.2a (n=1,043), subclade 3C.2a1 (n=143) or clade 3C.3a (n=88). Six hundred thirty-five influenza A(H3N2) viruses were antigenically characterized, and 596 (93.9%) A(H3N2) viruses tested were well-inhibited (reacting at titers that were within fourfold of the homologous virus titer) by ferret antisera raised against A/Michigan/15/2014 (3C.2a), a cell-propagated A/Hong Kong/4801/2014-like reference virus representing the A(H3N2) component of  2017–18 Northern Hemisphere influenza vaccines.

    Influenza B Viruses

    • B/Victoria: Phylogenetic analysis of 263 B/Victoria-lineage viruses indicate that all HA genes belonged to genetic clade V1A, the same genetic clade as the vaccine reference virus, B/Brisbane/60/2008. However, a number of viruses had a 6-nucleotide deletion (encoding amino acids 162 and 163) in the HA (abbreviated as V1A-2Del). Forty-six (24.9%) B/Victoria lineage viruses were well-inhibited by ferret antisera raised against cell-propagated B/Brisbane/60/2008 reference virus, representing a recommended B virus component of 2017–18 Northern Hemisphere influenza vaccines. One hundred thirty-nine (75.1%) B/Victoria lineage viruses reacted poorly (at titers that were 8-fold or greater reduced compared with the homologous virus titer) with ferret antisera raised against cell-propagated B/Brisbane/60/2008, and these viruses had the V1A-2Del HA.
    • B/Yamagata: Phylogenetic analysis of 846 influenza B/Yamagata-lineage viruses indicate that the HA genes belonged to clade Y3. A total of 738 influenza B/Yamagata-lineage viruses were antigenically characterized, and all were antigenically similar to cell-propagated B/Phuket/3073/2013, the reference vaccine virus representing the influenza B/Yamagata-lineage component of the 2017–18 Northern Hemisphere quadrivalent vaccines.

    The majority of U.S. viruses submitted for characterization come from state and local public health laboratories. Due to Right Size Roadmap considerations, specimen submission guidance to laboratories is that, if available, 2 influenza A(H1N1)pdm09, 2 influenza A(H3N2), and 2 influenza B viruses be submitted every other week. Therefore, the numbers of each virus type/subtype characterized should be more balanced across subtypes/lineages but will not reflect the actual proportion of circulating viruses. In the figure below, the results of tests performed by public health labs are shown on the left and CDC sequence results (by genetic clade/subclade) are shown on the right.


    Genetic Characterization
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    2018-2019 Influenza Season – U.S. Influenza Vaccine Composition:

    The World Health Organization (WHO) has recommended the Northern Hemisphere 2018-2019 influenza vaccine composition, and the Food and Drug Administration’s Vaccines and Related Biological Products Advisory Committee (VRBPAC) subsequently made the influenza vaccine composition recommendation for the United States. Both agencies recommend that influenza trivalent vaccines contain an A/Michigan/45/2015 (H1N1)pdm09-like virus, an A/Singapore/INFIMH-16-0019/2016 (H3N2)-like virus, and a B/Colorado/06/2017-like (B/Victoria lineage) virus. It is recommended that quadrivalent vaccines, which have two influenza B viruses, contain the viruses recommended for the trivalent vaccines, as well as a B/Phuket/3073/2013-like (B/Yamagata lineage) virus. The B recommendation represents a change in the influenza B/Victoria lineage component recommended for the 2017-2018 Northern Hemisphere and 2018 Southern Hemisphere influenza vaccines. The H3N2 recommendation represents an update to the 2017-2018 Northern Hemisphere vaccines, but not to the 2018 Southern Hemisphere vaccines which were recommended to include A/Singapore/INFIMH-16-0019/2016 (H3N2)-like virus. The B component change was made because of the detection and increasing global circulation of an antigenically drifted B/Victoria lineage virus. The update to the H3N2 component is not a result of antigenic drift, but because the egg-propagated A/Singapore vaccine virus is antigenically more similar to circulating viruses than the egg-propagated A/Hong Kong vaccine virus recommended for the Northern Hemisphere 2017-2018 vaccines. These vaccine recommendations were based on several factors, including global influenza virologic and epidemiologic surveillance, genetic characterization, antigenic characterization and the candidate vaccine viruses that are available for production.

    Antiviral Resistance:

    Testing of influenza A (H1N1)pdm09, influenza A (H3N2), and influenza B virus isolates for resistance to neuraminidase inhibitors (oseltamivir, zanamivir, and peramivir) is performed at CDC using a functional assay. Additional influenza A (H1N1)pdm09 and influenza A (H3N2) viruses from clinical samples are tested for mutations known to confer oseltamivir resistance. The data summarized below combine the results of both testing methods. These samples are routinely obtained for surveillance purposes rather than for diagnostic testing of patients suspected to be infected with antiviral-resistant virus.

    High levels of resistance to the adamantanes (amantadine and rimantadine) persist among influenza A (H1N1)pdm09 and influenza A (H3N2) viruses (the adamantanes are not effective against influenza B viruses). Therefore, data from adamantane resistance testing are not presented below.

    Neuraminidase Inhibitor Resistance Testing Results on Samples Collected Since October 1, 2017

     

    Oseltamivir

    Zanamivir

    Peramivir

     

    Virus Samples tested (n)

    Resistant Viruses, Number (%)

    Virus Samples tested (n)

    Resistant Viruses, Number (%)

    Virus Samples tested (n)

    Resistant Viruses, Number (%)

    Influenza A (H1N1)pdm09

    1,098

    11 (1.0)

    739

    0 (0.0)

    1,098

    11 (1.0)

    Influenza A (H3N2)

    2,322

    0 (0.0)

    2,322

    0 (0.0)

    1,216

    0 (0.0)

    Influenza B

    1,057

    0 (0.0)

    1,057

    0 (0.0)

    1,057

    0 (0.0)

    On December 27, 2017, a Health Advisory was released by CDC providing: 1) a notice about increased influenza A(H3N2) activity and its clinical implications; 2) a summary of influenza antiviral drug treatment recommendations; 3) an update about approved treatment drugs and supply this season; and 4) background information for patients about influenza treatment. More information is available at https://emergency.cdc.gov/han/han00409.asp.

    The majority of recently circulating influenza viruses are susceptible to the neuraminidase inhibitor antiviral medications, oseltamivir, zanamivir, and peramivir; however, rare sporadic instances of oseltamivir-resistant and peramivir-resistant influenza A(H1N1)pdm09 viruses and oseltamivir-resistant influenza A(H3N2) viruses have been detected worldwide. Antiviral treatment as early as possible is recommended for patients with confirmed or suspected influenza who have severe, complicated, or progressive illness; who require hospitalization; or who are at high risk for serious influenza-related complications. Additional information on recommendations for treatment and chemoprophylaxis of influenza virus infection with antiviral agents is available at http://www.cdc.gov/flu/antivirals/index.htm.



    Pneumonia and Influenza (P&I) Mortality Surveillance:

    Based on National Center for Health Statistics (NCHS) mortality surveillance data available on May 17, 2018, 6.0% of the deaths occurring during the week ending April 28, 2018 (week 17) were due to P&I. This percentage is below the epidemic threshold of 6.9% for week 17.

    Background: Weekly mortality surveillance data include a combination of machine coded and manually coded causes of death collected from death certificates.  Percentages of deaths due to P&I are higher among manually coded records than more rapidly available machine coded records. There is currently a delay in manual coding for deaths occurring in 2018.  Because of this delay initially reported P&I percentages will be lower than those calculated from the final data.

    Region and state-specific data are available at http://gis.cdc.gov/grasp/fluview/mortality.html.

    INFLUENZA Virus Isolated
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    Influenza-Associated Pediatric Mortality:

    Three influenza-associated pediatric deaths were reported to CDC during week 19. One death was associated with an influenza A(H1N1)pdm09 virus and occurred during week 16 (the week ending April 21, 2018). One death was associated with an influenza B virus and occurred during week 19 (the week ending May 12, 2018). One death was associated with an influenza virus for which type was not determined and occurred during week 14 (the week ending April 7, 2018).

    A total of 168 influenza-associated pediatric deaths have been reported for the 2017-2018 season.

    Additional data can be found at: http://gis.cdc.gov/GRASP/Fluview/PedFluDeath.html.

    Click on image to launch interactive tool

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    Influenza-Associated Hospitalizations:

    The Influenza Hospitalization Surveillance Network (FluSurv-NET) conducts population-based surveillance for laboratory-confirmed influenza-related hospitalizations in children younger than 18 years of age (since the 2003-2004 influenza season) and adults (since the 2005-2006 influenza season).

    The FluSurv-NET covers more than 70 counties in the 10 Emerging Infections Program (EIP) states (CA, CO, CT, GA, MD, MN, NM, NY, OR, and TN) and additional Influenza Hospitalization Surveillance Project (IHSP) states. The IHSP began during the 2009-2010 season to enhance surveillance during the 2009 H1N1 pandemic. IHSP sites included IA, ID, MI, OK and SD during the 2009-2010 season; ID, MI, OH, OK, RI, and UT during the 2010-2011 season; MI, OH, RI, and UT during the 2011-2012 season; IA, MI, OH, RI, and UT during the 2012-2013 season; and MI, OH, and UT during the 2013-2014, 2014-15, 2015-16, 2016-17, and 2017-18 seasons.

    Data gathered are used to estimate age-specific hospitalization rates on a weekly basis, and describe characteristics of persons hospitalized with influenza illness. The rates provided are likely to be an underestimate as influenza-related hospitalizations can be missed, either because testing is not performed, or because cases may be attributed to other causes of pneumonia or other common influenza-related complications.

    A total of 30,451 laboratory-confirmed influenza-associated hospitalizations were reported between October 1, 2017 and April 30, 2018. The overall hospitalization rate was 106.6 per 100,000 population. The highest rate of hospitalization was among adults aged ≥65 years (460.3 per 100,000 population), followed by adults aged 50-64 (115.8 per 100,000 population) and children aged 0-4 years (74.7 per 100,000 population). Among 30,451 hospitalizations, 22,062 (72.5%) were associated with influenza A virus, 8,169 (26.8%) with influenza B virus, 112 (0.4%) with influenza A virus and influenza B virus co-infection, and 108 (0.4%) with influenza virus for which the type was not determined. Among those with influenza A subtype information, 6,068 (84.3%) were A(H3N2) and 1,133 (15.7%) were A(H1N1)pdm09 virus.

    Among 6,125 hospitalized adults with information on underlying medical conditions, 5,660 (92.4%) had at least one reported underlying medical condition; the most commonly reported were cardiovascular disease, metabolic disorder, obesity, and chronic lung disease. Among 608 hospitalized children with information on underlying medical conditions, 346 (56.9%) had at least one underlying medical condition; the most commonly reported were asthma, neurologic disorder, and obesity. Among 530 hospitalized women of childbearing age (15-44 years) with information on pregnancy status, 163 (30.8%) were pregnant.

    While patients admitted after April 30, 2018 will not be included, data on patients admitted through April 30, 2018 will continue to be updated as additional information is received.

    Additional FluSurv-NET data can be found at: http://gis.cdc.gov/GRASP/Fluview/FluHospRates.html and http://gis.cdc.gov/grasp/fluview/FluHospChars.html.


    Click on graph to launch interactive tool

    Data from the Influenza Hospitalization Surveillance Network (FluSurv-NET), a population-based surveillance for influenza related hospitalizations in children and adults in 13 U.S. states. Cumulative incidence rates are calculated using the National Center for Health Statistics’ (NCHS) population estimates for the counties included in the surveillance catchment area.

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    Click on graph to launch interactive tool2

    FluSurv-NET data are preliminary and displayed as they become available. Therefore, figures are based on varying denominators as some variables represent information that may require more time to be collected. Data are refreshed and updated weekly. Asthma includes a medical diagnosis of asthma or reactive airway disease; Cardiovascular diseases include conditions such as coronary heart disease, cardiac valve disorders, congestive heart failure, and pulmonary hypertension; does not include isolated hypertension; Chronic lung diseases include conditions such as chronic obstructive pulmonary disease, bronchiolitis obliterans, chronic aspiration pneumonia, and interstitial lung disease; Immune suppression includes conditions such as immunoglobulin deficiency, leukemia, lymphoma, HIV/AIDS, and individuals taking immunosuppressive medications; Metabolic disorders include conditions such as diabetes mellitus; Neurologic diseases include conditions such as seizure disorders, cerebral palsy, and cognitive dysfunction; Neuromuscular diseases include conditions such as multiple sclerosis and muscular dystrophy; Obesity was assigned if indicated in patient's medical chart or if body mass index (BMI) >30 kg/m2; Pregnancy percentage calculated using number of female cases aged between 15 and 44 years of age as the denominator; Renal diseases include conditions such as acute or chronic renal failure, nephrotic syndrome, glomerulonephritis, and impaired creatinine clearance; No known condition indicates that the case did not have any known high risk medical condition indicated in medical chart at the time of hospitalization.

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    Outpatient Illness Surveillance:

    Nationwide during week 19, 1.2% of patient visits reported through the U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet) were due to influenza-like illness (ILI). This percentage is below the national baseline of 2.2%. (ILI is defined as fever (temperature of 100°F [37.8°C] or greater) and cough and/or sore throat.)

    Additional ILINet data, including national, regional and select state-level data, are available at http://gis.cdc.gov/grasp/fluview/fluportaldashboard.html.

    national levels of ILI and ARI
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    On a regional level, the percentage of outpatient visits for ILI ranged from 0.5% to 2.1% during week 19.  All 10 regions reported a percentage of outpatient visits for ILI below their region-specific baselines.



    ILINet State Activity Indicator Map:

    Data collected in ILINet are used to produce a measure of ILI activity* by state. Activity levels are based on the percent of outpatient visits in a state due to ILI and are compared to the average percent of ILI visits that occur during weeks with little or no influenza virus circulation. Activity levels range from minimal, which would correspond to ILI activity from outpatient clinics being below, or only slightly above, the average, to high, which would correspond to ILI activity from outpatient clinics being much higher than average.

    During week 19, the following ILI activity levels were experienced:

    • New York City, the District of Columbia, Puerto Rico and all 50 states experienced minimal ILI activity.
    Click on map to launch interactive tool

    *This map uses the proportion of outpatient visits to health care providers for ILI 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 disproportionally represent certain populations within a state, and therefore, may not accurately depict the full picture of influenza activity for the whole state.
    Data displayed in this map are based on data collected in ILINet, whereas the State and Territorial flu activity map is based on reports from state and territorial epidemiologists. The data presented in this map are preliminary and may change as more data are received.
    Differences in the data presented here by CDC and independently by some state health departments likely represent differing levels of data completeness with data presented by the state likely being the more complete.



    Geographic Spread of Influenza as Assessed by State and Territorial Epidemiologists

    The influenza activity reported by state and territorial epidemiologists indicates geographic spread of influenza viruses, but does not measure the severity of influenza activity.

    Additional data can be found at https://gis.cdc.gov/grasp/fluview/FluView8.html.

    During week 19, the following influenza activity was reported:

    • Widespread influenza activity was reported by two states (Massachusetts and New York).
    • Regional influenza activity was reported by Guam, Puerto Rico and three states (Connecticut, Kentucky, and Maine).
    • Local influenza activity was reported by nine states (Alaska, Arizona, Michigan, Minnesota, New Jersey, Ohio, Utah, Vermont, and Wisconsin).
    • Sporadic influenza activity was reported by the District of Columbia, the U.S. Virgin Islands and 33 states (Arkansas, California, Colorado, Delaware, Florida, Georgia, Hawaii, Idaho, Illinois, Indiana, Iowa, Kansas, Louisiana, Maryland, Missouri, Montana, Nebraska, Nevada, New Mexico, New Hampshire, North Carolina, North Dakota, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Texas, Virginia, Washington, West Virginia, and Wyoming).
    • No influenza activity was reported by three states (Alabama, Mississippi, and Tennessee).


    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. To access these tools, visit http://www.cdc.gov/flu/weekly/fluviewinteractive.htm.

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

    Alabama

    Alaska

    Arizona

    Arkansas

    California

    Colorado

    Connecticut

    Delaware

    District of Columbia

    Florida

    Georgia

    Hawaii

    Idaho

    Illinois

    Indiana

    Iowa

    Kansas

    Kentucky

    Louisiana

    Maine

    Maryland

    Massachusetts

    Michigan

    Minnesota

    Mississippi

    Missouri

    Montana

    Nebraska

    Nevada

    New Hampshire

    New Jersey

    New Mexico

    New York

    North Carolina

    North Dakota

    Ohio

    Oklahoma

    Oregon

    Pennsylvania

    Rhode Island

    South Carolina

    South Dakota

    Tennessee

    Texas

    Utah

    Vermont

    Virginia

    Washington

    West Virginia

    Wisconsin

    Wyoming

    New York City

    Puerto Rico

    Virgin Islands



    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 located in Australia, China, Japan, the United Kingdom, and the United States (CDC in Atlanta, Georgia).

    Europe: For the most recent influenza surveillance information from Europe, please see WHO/Europe and the European Centre for Disease Prevention and Control at http://www.flunewseurope.org/.

    Public Health Agency of Canada: The most up-to-date influenza information from Canada is available at http://www.phac-aspc.gc.ca/fluwatch/

    Public Health England: The most up-to-date influenza information from the United Kingdom is available at https://www.gov.uk/government/statistics/weekly-national-flu-reports



    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.

    An overview of the CDC influenza surveillance system, including methodology and detailed descriptions of each data component, is available at: http://www.cdc.gov/flu/weekly/overview.htm.

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