Fourth, our estimate of influenza-associated deaths relies on information about location of death from death certificates to calculate ratios of deaths occurring in the hospital to deaths occurring outside of the hospital by categories of causes of death. However children less than 5 years old also reported a relevant influenza attributable excess death rate in the 2014/15 and 2016/17 seasons (1.05/100,000 and 1.54/100,000 respectively). First, rates of influenza-associated hospitalizations are based on data reported to the Influenza Hospitalization Surveillance Network (FluSurv–NET) through September 2, 2020. But news reports and the World Health Organization often estimate it at around 0.1%. However, influenza-associated pediatric deaths are likely under-reported as not all children whose death was related to an influenza virus infection may have been tested for influenza9,10. These estimates will change as those data become available and the estimates are updated. Influenza deaths in 2019 and 2020 . Estimates of influenza-associated mortality were of similar magnitude. Seasonal influenza 2018–2019 Annual Epidemiological Report Key facts Influenza activity started in week 49/2018, peaked in week 7/2019 and returned to baseline levels in week 17/2019. Die Influenza, auch (echte) Grippe oder Virusgrippe genannt, ist eine überwiegend durch Viren aus der Gruppe der Orthomyxoviridae und den Gattungen Influenzavirus A oder B ausgelöste Infektionskrankheit bei Menschen. Saving Lives, Protecting People, Benefits of Flu Vaccination for the 2019-2020 Season, More answers to frequently asked questions about CDC’s influenza burden estimates are available, http://dx.doi.org/10.15585/mmwr.mm6937a6n, https://www.cdc.gov/flu/weekly/fluactivitysurv.htm, https://www.cdc.gov/flu/about/burden/past-seasons.html, Centers for Disease Control and Prevention, National Center for Immunization and Respiratory Diseases (NCIRD), Reconstruction of the 1918 Influenza Pandemic Virus, 2019-2020 Preliminary In-Season Burden Estimate, Who is at High Risk for Flu Complications, Who Should & Who Should NOT Get Vaccinated, Live Attenuated Influenza Vaccine (LAIV)/Nasal Spray Vaccine, Selecting Viruses for the Seasonal Influenza Vaccine, Flu Vaccine and People with Egg Allergies, Frequently Asked Questions on Vaccine Supply, Historical Reference of Vaccine Doses Distributed, Hospitalized Adult Influenza Vaccine Effectiveness Network (HAIVEN), How Vaccine Effectiveness and Efficacy are Measured, What People with a Staph Infection Should Know about Flu, Resources for Hosting a Vaccination Clinic, Overview of Influenza Surveillance in the United States, Influenza Hospitalization Surveillance Network (FluSurv-NET), Weekly U.S. 2020 weekly updates; 2019 weekly updates; 2018 weekly updates; 2017 weekly updates; 2016 weekly updates; 2015 weekly updates; 2014 weekly updates; … These frequencies were not available from the 2018–2019 season at the time of estimation, so we used the average frequencies of each cause from previous seasons, 2010–2011 to 2016–2017. That is longer than the average period of nine weeks during the last 20 years, but it is shorter than the extended influenza epidemic of 2017/2018 which lasted 18 weeks. ICD-9 BTL codes: B322 ICD-9 codes: 487 ICD-10 codes: J10-J11 ex-USSR 175 list: 104 ICD-10 Mortality Condensed list 1: 1073 EUROSTAT list of 65 causes: 38 SDR is the age-standardized death rate calculated using the direct method and standard European population structure. These multipliers are based on data from a prior season, which may not be accurate if patterns of care-seeking have changed. A nurse wears a cloth mask while treating a patient in Washington, DC . : +45 45 33 70 00 Third, estimates of influenza-associated illness and medical visits are based on a ratio of illnesses to hospitalizations determined in a prior study. 1. However, data on testing practices during the 2018–2019 season were not available at the time of estimation. Data to generate these frequencies were not available from the 2019–2020 season at the time of estimation, so we used the average frequencies of location of death for each of the cause categories from previous seasons, 2010–2011 through 2017–2018. We adjusted rates using the lowest multiplier from any season between 2010–2011 and 2017–2018. However, it is useful to keep in mind that direct comparisons to influenza disease burden decades ago are complicated by large differences in the age of the US population and the increasing number of adults aged ≥65 years. The highest age-specific mortality rate was observed in those aged 85 years and over, with 1,744.3 deaths per 100,000 people. CDC estimates that influenza was associated with more than 35.5 million illnesses, more than 16.5 million medical visits, 490,600 hospitalizations, and 34,200 deaths during the 2018–2019 influenza season. In addition to expected changes in available data on testing practices and patients hospitalized for flu, there were unexpected data delays due to the onset of the COVID-19 pandemic in Spring 2020. Influenza/Influenza-like Illness (ILI) Activity (geographic spread) Yearly influenza immunization rates. Excepting cases in Hubei, the mortality rate dropped down to 0.16 percent, bringing it much closer to the flu. Alltagssprachlich wird die Bezeichnung Grippe häufig auch für grippale Infekte, Erkältung oder Verkühlung verwendet, bei denen es sich aber um verschiedene andere, in der Regel deutlich harmloser verlaufende (insof… We adjusted rates using the most conservative multiplier from any season between 2010–2011 and 2016–2017. 22,000 flu deaths, enough people to fill Madison Square Garden in New York City. The methods used to calculate the estimates have been described previously (1-2). During the 2018–2019 season, 136 deaths in children with laboratory–confirmed influenza virus infection were reported in the United States8. However children less than 5 years old also reported a relevant influenza attributable excess death rate in the 2014/15 and 2016/17 seasons (1.05/100,000 and 1.54/100,000 respectively). The Y axis goes to 1%. Understanding the burden of influenza-associated mortality is crucial for public health decision making, both nationally and internationally. Linking to a non-federal website does not constitute an endorsement by CDC or any of its employees of the sponsors or the information and products presented on the website. There is no evidence of significant excess mortality at this early stage, however experience during past seasons suggests a significant mortality impact on ... mortality for public health action). View the retrospective 2017 to 2018 data. These estimates are subject to several limitations. For 92 countries, we estimated that among children younger than 5 years, 9243-105 690 influenza-associated respiratory deaths occur annually. Weekly influenza updates for the period 2003 - 2013 Weekly electronic bulletins (2003-2009) The Weekly Electronic Bulletin was written by the European Influenza Surveillance Scheme Co-ordination Centre from the 2003–04 to the 2008–09 season. However, each season’s estimates will be finalized when data on testing practices and deaths for that season are available. Differences: COVID-19 and the Flu Cause. *2017–2018, 2018–2019, and 2019–2020 are preliminary estimates. While the medical community is still learning about mortality from COVID-19, it does appear to be more deadly than the flu. Select format (Excel or CSV for example) This will provide you with a dataset showing the number of deaths from influenza in 2019. CDC uses the estimates of the burden of influenza in the population to inform policy and communications related to influenza. Flu: Caused by any of several different types and strains of influenza viruses.Different strains circulate each year. CDC estimates that influenza was associated with more than 35.5 million illnesses, more than 16.5 million medical visits, 490,600 hospitalizations, and 34,200 deaths during the 2018–2019 influenza season. More than 46,000 hospitalizations occurred in children (aged <18 years); however, 57% of hospitalizations occurred in older adults aged ≥65 years. During the 2019-2020 flu season, CDC estimates flu caused: 38 million flu illnesses, about the same as the population of California. For these estimates, we included additional information to better capture flu testing practices at sites in the hospital-based surveillance system, FluSurv-NET, that collects data on patients hospitalized with laboratory-confirmed flu. Seasonal influenza is an acute respiratory infection caused by influenza viruses which circulate in all parts of the world. Freedom of Information | Released on 8 September 2020 Influenza deaths in 2018, 2019 and 2020 . CDC twenty four seven. Care 230 influenza women and In the temperate zones of the southern hemisphere, influenza activity returned to interseasonal levels. This makes it difficult to directly compare our estimates for seasons since 2009 to those older reports, though the estimates from our current method are largely consistent with estimates produced with statistical models for similar years (12–13). 50 30 40 Syndromic surveillance o Syndromic surveillance indicators for influenza remained low, in weeks 37 and 38 2019. o For further information, please see the Syndromic surveillance webpage. Final case counts may differ slightly as further data cleaning from the 2019-2020 season are conducted by FluSurv–NET sites. More than 52,000 hospitalizations occurred in children aged < 18 years and 86,000 hospitalizations among adults aged 18-49 years. Second, rates of laboratory-confirmed influenza-associated hospitalizations were adjusted for the frequency of influenza testing and the sensitivity of influenza diagnostic assays. Influenza season 2019 ... are already seeing increased rates of influenza hospitalisation. Comparing COVID-19 and 2020 influenza and pneumonia mortality rates, the largest absolute difference in rates was found in those aged 85 years and over, with a difference of 712.9 deaths per 100,000 people. COVID-19: Many people infected with the coronavirus do not feel sick or have any symptoms at all, but they can still transmit the coronavirus to … In contrast, Japan and Taiwan had reported a mortality rate from influenza around 0.45% and 0.69% respectively, higher than the mortality rate collected from data in Chinese port cities, such as Hong Kong (0.25%), Canton (0.32%), and Shanghai. The 2019–2020 influenza season was atypical in that it was severe for children aged 0-4 years and adults 18-49 years where rates of infections, medically attended illnesses, hospitalizations, and deaths were higher than those observed during the 2017-2018 season, a recent season with high severity (7). To receive weekly email updates about Seasonal Flu, enter your email address: Centers for Disease Control and Prevention. during the 2019–2020 season, ILI and COVID-19-like illness (CLI) followed similar weekly incidence rate trends, although absolute values were different, as shown by the National Syndromic Surveillance Program in USA [23], and the general practitioners’ network in France [24]. The Centers for Disease Control and Prevention (CDC) cannot attest to the accuracy of a non-federal website. Age-specific death rates decreased from 2018 to 2019 . Second, national rates of influenza-associated hospitalizations and in-hospital death were adjusted for the frequency of influenza testing and the sensitivity of influenza diagnostic assays, using a multiplier approach3. The additional mortality data from FluSurv-NET are typically not available for up to 2 years after the end of a flu season. To provide timely burden estimates to the public, clinicians, and public health decision-makers, CDC uses preliminary data that may lead to over- or under-estimates of the true burden. Surveillance of influenza and other respiratory infections: winter 2018/2019 Influenza epidemic The influenza epidemic of the 2018/2019 winter was mild and lasted 14 weeks. However, influenza-associated pediatric deaths are likely under-reported, as not all children whose death was related to an influenza virus infection may have been tested for flu (10,11). You will be subject to the destination website's privacy policy when you follow the link. This makes it difficult to directly compare our estimates since 2009 to those older reports, though the estimates from our current method are largely consistent for similar years12–15. Please also see the following dataset: Deaths registered in England and Wales. More answers to frequently asked questions about CDC’s influenza burden estimates are available. Based on NCHS mortality surveillance data available on April 1, 2021, 11.4% of the deaths that occurred during the week ending March 27, 2021 (week 12), were due to pneumonia, influenza, and/or COVID-19 (PIC). Figure 2 – Number of positive influenza tests and percentage of positive tests, by type, subtype and report week, Canada, weeks 2018-35 to 2019-34. We used death certification data from all influenza seasons from 2010–2011 through 2017–2018 where these data were available from the National Center for Health Statistics. Read the review in the Weekly epidemiological record; Archives. Read the review in the Weekly epidemiological record Summary – Week 51 (ending 22 December 2019) week. When additional data become available, these estimates will be updated again, and the results may change. Influenza Surveillance Report (FluView), Past Flu Seasons Flu Forecasting Accuracy Results, Tools to Prepare Your Practice for Flu Season, Information for Clinicians on Influenza Virus Testing, Multiplex Assays Authorized for Simultaneous Detection of Influenza Viruses and SARS-CoV-2, Information on Collection of Respiratory Specimens for Influenza Virus Testing, Information for Clinicians on Rapid Diagnostic Testing for Influenza, Information on Rapid Molecular Assays, RT-PCR, and other Molecular Assays for Diagnosis of Influenza Virus Infection, Algorithm: Interpreting Influenza Testing Results When Influenza is Circulating, Algorithm: Interpreting Influenza Testing Results When Influenza is NOT Circulating, Guide: Influenza Diagnostic Testing in Closed Setting Outbreaks, Guidance: Standard-Based Electronic Laboratory Reporting, Guidance: Antiviral and Obstetric Health Care, Guidance: Outbreak Management in Long-Term Care Facilities, Guidance: Use of Mask to Control Influenza Transmission, Guidance: Prevention & Control in Peri- and Postpartum Settings, Health Professional References & Resources, Responding to Problems with Purchasing Needles for Flu Vaccination, U.S. Department of Health & Human Services. Primary Care In week 50, the rate of influenza-like illness (ILI) continues … This burden was similar to estimated burden during the 2012–2013 influenza season1. The infant mortality rate in. The season was characterized by two consecutive waves of activity, beginning with influenza B viruses and followed by A(H1N1)pdm09 viruses. Lost in the discussion about COVID-19 is the fact that the US is experiencing a severe influenza season that has already resulted in more than 16 000 deaths. While influenza A(H1N1pdm09) viruses predominated from October 2018 – mid February 2019, influenza A(H3N2) viruses were more commonly reported starting in late February 2019. These testing data are often not available for up to 2 years after the end of a flu season, and thus the burden estimates are revised when additional testing data become available. A total of 19,713 influenza-related hospitalizations were reported between October 1, 2019 and March 28, 2020. The methods used to calculate these estimates are described on CDC’s webpage, How CDC Estimates the Burden of Seasonal Influenza in th… Burden estimates from the 2019–2020 season will be updated at a later date when data on contemporary testing practices become available. The pathogen. Every year we encourage more Albertans to get immunized. for age groups 45–54, 65–74, 75–84, and 85 and over. Influenza season 2019 ... are already seeing increased rates of influenza hospitalisation. Burden estimates from the 2018–2019 season will be updated at a later date when data on contemporary testing practices become available. Due to the 2017 to 2018 data issues described in our 2018 to 2019 ILI technical document, the ILI data included on the weekly reports has been revised. The Centers for Disease Control and Prevention (CDC) cannot attest to the accuracy of a non-federal website. Fifth, estimates of burden were derived from rates of influenza-associated hospitalization, which is a different approach than the statistical models used in older published reports. Influenza viruses circulated at high levels between weeks 52/2018 and 12/2019. These symptoms typically begin 1–4 … In 1920, the mortality rate among people under 65 had decreased sixfold to half the mortality rate of people over 65, but 92% of deaths still occurred in people under 65. Mortality for COVID-19 appears higher than for influenza, especially seasonal influenza. These rates mean that an estimated 15 million cases of influenza in younger adults (aged 18-49 years), which is the highest number of infections for this age group since CDC began reporting influenza burden estimates in the 2010-11 season. CDC’s estimates of hospitalizations and mortality associated with the 2019–2020 influenza season show the effects that influenza virus infections can have on society. The case fatality rate for influenza will obviously change year to year. Thus, reports of laboratory-confirmed flu-related hospitalizations to FluSurv-NET are underestimates of the true number of hospitalizations. These estimates are an update to the preliminary in-season 2019-20 burden estimates published April 2020 and are based on more recently available information. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. From the Centers for Disease Control and Preventionpage called "Disease Burden of Influenza": "Each year CDC estimates the burden of influenza in the U.S. CDC uses modeling to estimate the number of influenza illnesses, medical visits, flu-associated hospitalizations, and flu-associated deaths that occur in the U.S. in a given season. However, data on testing practices during the 2019–2020 season were not available at the time of estimation. Deaths in children with laboratory-confirmed influenza virus infection have been a reportable disease in the United States since 2004; 188 deaths were reported for the 2019-20 season as of September 19, 2020. To calculate these ratios, first we calculate the frequency of flu-related deaths reported from our FluSurv-NET surveillance system that have cause of death identified as pneumonia or influenza (P&I), other respiratory or cardiovascular (other R&C), or other non-respiratory, non-cardiovascular (non-R&C). These findings continue to highlight that older adults are particularly vulnerable to severe disease with influenza virus infection. This has led the Quarter 1 2019 mortality rate to be statistically significantly lower than all years, except 2014, which was a notably low year for mortality and had the same rate for all persons in 2019. US influenza statistics by flu season. The current estimates were made using the highest testing rate for each age-group from the 2010-2011 through the 2017-2018 seasons. However, it is useful to keep in mind that direct comparisons to influenza disease burden decades ago are complicated by large differences in the age of the US population and the increasing number of adults aged ≥65 years. Human infectious diseases may be characterized by their case fatality rate (CFR). First, rates of influenza-associated hospitalizations are based on data reported to the Influenza Hospitalization Surveillance Network (FluSurv–NET) through October 1, 2019. Division of Information, Evidence, Research and Innovation WHO Regional Office for Europe UN City Marmorvej 51 DK-2100 Copenhagen Ø Denmark Tel. An estimated 8,100 deaths occurred among working age adults (aged 18–64 years), an age group that often has low influenza vaccination uptake11. Older adults also accounted for 62% of deaths, which is lower than recent previous seasons. At the national level, notifications of laboratory-confirmed inf… However, data from FluSurv-NET that is usually available at the end of flu season was delayed in 2020 due to the onset of the COVID-19 pandemic. FDA Approval and Regulation of Pharmaceuticals, 1983-2018 Global Burden of Cancer, 1990-2017 Global Burden of Skin Diseases, 1990-2017 Global Firearm Mortality, 1990-2016 Health Care Spending in the US and Other High-Income Countries Life Expectancy and Mortality Rates in the United States, 1959-2017 Medical Marketing in the United States, 1997-2016 Practices to Foster Physician … Includes analysis of … A separate tracker from coronavirus.app revealed 436,200 people … The PHE report published at 2pm on 3 January 2019 suggests that influenza is starting to circulate in the community and is at moderate levels. 2019 of 558.3 infant deaths per 100,000 live births did not change significantly from the rate … Therefore, we used a mathematical model to estimate the total number of pediatric deaths based on hospitalization rates and the frequency of death in and out of the hospital using death certificates. This ratio is based on data from prior seasons, which may not be accurate if patterns of care-seeking have changed. Around 15 million people were vaccinated against the flu in 2019. Next, to account for deaths occurring outside of a hospital, we use information from national death certificates to calculate the proportion of deaths from these causes that occur in and out of the hospital. This web page provides estimates on the burden of influenza (flu) in the United States for the 2019–2020 flu season. This burden was similar to estimated burden during the 2012–2013 influenza season1. There are 4 types of seasonal influenza viruses, types A, B, C and D. Influenza A and B viruses circulate and cause seasonal epidemics of disease.. Symptoms. Select format (Excel or CSV for example) This will provide you with a dataset showing the number of deaths from influenza in 2019. Estimated Influenza Disease Burden – United States [1] The vast majority of influenza viruses detected were type A. Select cause of death (ICD10 code search is available). The 2019-2020 estimates that are presented here remain preliminary because not all of the data needed for final estimates are available. Activity– Currently, influenza and influenza-like illness (ILI) activity is lower than average for this time of year compared to previous years, and is consistent with past activity following a peak in notifications and coming to the end of the influenza season. Although a great deal of attention has been given to the coronavirus disease 2019 (COVID-19) epidemic, it is most severe in one area of China and appears to have limited clinical ramifications outside of that region. *Some of the data used to calculate burden estimates are incomplete or not yet available. The methods used to calculate the estimates have been described previously3. 72% were associated with Influenza A and 27% were Influenza B, which is a reversal of early season numbers when Influenza B was more dominant. The number of cases of influenza-associated illness, medically attended illnesses, hospitalizations, and deaths were lower than some more recent seasons and similar to other seasons where influenza A(H1N1)pdm09 viruses dominated (7, 8). CDC estimates that the burden of illness during the 2018–2019 season included an estimated 35.5 million people getting sick with influenza, 16.5 million people going to a health care provider for their illness, 490,600 hospitalizations, and 34,200 deaths from influenza (Table 1). Mortality for COVID-19 appears higher than for influenza, especially seasonal influenza. This report summarizes the 2018-2019 influenza season in the temperate regions of the northern hemisphere. Influenza Surveillance Report (FluView), Past Flu Seasons Flu Forecasting Accuracy Results, Tools to Prepare Your Practice for Flu Season, Information for Clinicians on Influenza Virus Testing, Multiplex Assays Authorized for Simultaneous Detection of Influenza Viruses and SARS-CoV-2, Information on Collection of Respiratory Specimens for Influenza Virus Testing, Information for Clinicians on Rapid Diagnostic Testing for Influenza, Information on Rapid Molecular Assays, RT-PCR, and other Molecular Assays for Diagnosis of Influenza Virus Infection, Algorithm: Interpreting Influenza Testing Results When Influenza is Circulating, Algorithm: Interpreting Influenza Testing Results When Influenza is NOT Circulating, Guide: Influenza Diagnostic Testing in Closed Setting Outbreaks, Guidance: Standard-Based Electronic Laboratory Reporting, Guidance: Antiviral and Obstetric Health Care, Guidance: Outbreak Management in Long-Term Care Facilities, Guidance: Use of Mask to Control Influenza Transmission, Guidance: Prevention & Control in Peri- and Postpartum Settings, Health Professional References & Resources, Responding to Problems with Purchasing Needles for Flu Vaccination, U.S. Department of Health & Human Services. The most updated crude rates of hospitalization for FluSurv-NET sites from the 2018–2019 season are available on FluView Interactive7. Final case counts may differ slightly as further data cleaning from the 2018–2019 season are conducted by FluSurv–NET sites. The most updated crude rates of hospitalization for FluSurv-NET sites are available on FluView Interactive (6). We have used death certification data from all influenza seasons between 2010-2011 and 2016–2017  where these data were available from the National Center for Health Statistics. What is the typical peak month for influenza deaths? The average annual mortality excess rate per 100,000 ranged from 11.6 to 41.2 with most of the influenza-associated deaths per year registered among the elderly. The average annual mortality excess rate per 100,000 ranged from 11.6 to 41.2 with most of the influenza-associated deaths per year registered among the elderly. There is a trade-off between timeliness and accuracy of burden of disease estimates. Despite some of the most severe restrictions ever endured by the UK, there has been an … 400,000 flu hospitalizations, about the same as the population of Miami, FL. For the past several years, CDC has used a mathematical model to estimate the numbers of influenza illnesses, medical visits, hospitalizations, and deaths (1-4). A CFR is the proportion of people diagnosed with a disease who die from the disease (cf. Second, national rates of influenza-associated hospitalizations and in-hospital death were adjusted for the frequency of influenza testing and the sensitivity of influenza diagnostic assays, using a multiplier approach (3). Influenza mortality in symptomatic cases in the US for the 2018/2019 season. Influenza viruses circulated at high levels between weeks 52/2018 and 12/2019. In the Lancet Public Health, the population-based modelling study by Li Li and colleagues1 on influenza-associated excess respiratory mortality in mainland China contributes an essential piece to the global picture of influenza-associated mortality. Influenza B viruses were not commonly reported among circulating viruses during the 2018–2019 season. CDC is not responsible for Section 508 compliance (accessibility) on other federal or private website. View the reporting rates of influenza-like illness (ILI) consultations from General Practitioners in Scotland technical document. You will be subject to the destination website's privacy policy when you follow the link. CDC estimates that the burden of illness during the 2019–2020 season was moderate with an estimated 38 million people sick with flu, 18 million visits to a health care provider for flu, 400,000 hospitalizations for flu, and 22,000 flu deaths  (Table 1). While the medical community is still learning about mortality from COVID-19, it does appear to be more deadly than the flu. Patterns of fatality. The burden of influenza and the rates of influenza-associated hospitalization are usually higher for the very young and the very old, and while this was observed during the 2019–2020 season, rates of hospitalization in adults aged 18-49 years were the highest seasonal rates seen since the 2017-2018 season (Table 2). The method used to estimate flu-related deaths relies on additional data from FluSurv-NET and the National Center for Health Statistics (NCHS) (data on cause of death and numbers of deaths that occur inside versus outside of the hospital). adopted a similar step-wise method to extrapolate influenza-associated respiratory excess mortality rates for provinces in mainland China without valid data for a direct estimation. Flu testing is done at the request of individual clinicians, but not everyone is tested, and flu tests are not perfectly accurate. But news reports and the World Health Organization often estimate it at around 0.1%. This is unusual since influenza is typically most deadly to weak individuals, such as infants under age two, adults over age 70, and the immunocompromised . Analysis of the characteristics of people who died from the coronavirus (COVID-19), compared with people who died from influenza (flu) and pneumonia. leading cause and influenza and pneumonia, the ninth in 2019, switched ranks. This information is used to correct for the underestimates of flu-related hospitalizations. Influenza, commonly called "the flu", is an infectious disease caused by influenza viruses. Influenza A viruses were the predominant circulating viruses last year. 2019 to 2020 – 33%; 2018 to 2019 – 31%; 2017 to 2018 – 29%; 2016 to 2017 – 27%; 2015 to 2016 – 27%; 2014 to 2015 – 30%; 2013 to 2014 – 27.6%; 2012 to 2013 – 23%; 2011 to 2012 – 22.5%; 2010 to 2011 – 22% ; Health care worker immunization.