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Health Indicator Report of Influenza Virus Infections

Influenza (flu) is a very contagious viral infection of the nose, throat, bronchial tubes, and lungs. Influenza is a respiratory infection and does not typically involve gastrointestinal symptoms. In some very young children the infection can cause gastrointestinal symptoms. It is estimated that nearly 16 million to 63 million U.S. residents get influenza each year and about 200,000 of them are hospitalized. The estimated annual death toll from complications associated with the disease ranges from 3,000 to 49,000. Influenza viruses are classified into types A, B, and C. Influenza type A and B viruses typically cause the most serious illnesses. Type A viruses are usually the cause of the most serious epidemics, and the most severe illness (influenza-associated hospitalizations). Type B viruses can cause epidemics, but illness is usually milder than illnesses caused by type A viruses. Type C is less common and typically only causes mild illness in humans. Each type of influenza includes many different strains which tend to change each year. Due to the fact that the strains can change each year, people do not build resistance, or immunity, to the next upcoming influenza strain. Every year, 9 to 10 months before the next influenza ("flu") season, scientists begin to prepare a new vaccine. Influenza vaccines include inactivated or killed virus from both A and B strains. People who have influenza can make you sick if they cough or sneeze near you. The viruses can pass through the air and enter your body through your nose or mouth. Influenza can also be spread if you touch things like a telephone or doorknob that has been contaminated by someone who has influenza. If you touch a contaminated surface and touch your eyes, nose, or mouth without washing your hands, you can become sick. Most people recover from influenza within one week, however, some have life-threatening complications, such as pneumonia, and may need to be hospitalized. In fact, most influenza-related deaths are due to pneumonia. There are certain populations that are at risk for severe complications of influenza. These populations include the elderly (65 years of age and older), children less than 24 months old, those with chronic respiratory and cardiovascular disease, and those with chronic metabolic disease such as diabetes. During the 2014-2015 influenza season, approximately 1,400 Utah residents were hospitalized due to influenza-associated hospitalizations. Nearly 1 in 12 Utah resident deaths (7.8%) had pneumonia and/or influenza listed as the cause of death. The 2009 H1N1 pandemic caused a lot of sickness in Utah. From June of 2009 until September 2010, over 1,300 hospitalizations and 45 deaths due to H1N1 were reported in Utah. The H1N1 strain of the influenza virus affected the population differently than what is seen during a typical influenza season. Generally during an influenza season it is the very young and very old most affected, but with 2009 H1N1 influenza two-thirds, or roughly 67%, of all cases were in individuals aged 5 to 64 years. Within the most recent influenza season (2014-2015) a majority of cases occurred during the months of December through February with most cases testing positive for a mutated, or "drifted", strain of influenza A, H3 virus that was not included in the season's vaccine. In many cases, the body's immune system may not recognize these newer strains because they have "drifted" in disease causing properties from the old strains. Influenza B persisted through the end of the 2014-2015 season.

Number of Influenza Virus Infections per 100,000 Population by Year, Utah, 2010-2015


Graphs with influenza surveillance data are located at [].

Data Source

Utah Department of Health, Bureau of Epidemiology


Since influenza surveillance comprises several components, multiple definitions are used when describing influenza activity, including the following: number of visits for influenza-like illness (ILI) at sentinel sites, laboratory-confirmed cases, influenza-associated hospitalizations, and student absences from sentinel schools. Confirmation of an influenza case relies on laboratory testing using one of the following tests: Realtime PCR (RT-PCR), Direct Fluorescence Antibody (DFA), rapid influenza tests, serological tests, and/or viral culture. For seasonal influenza data collected by the Utah Department of Health, please visit []. Reports available include weekly updates and annual seasonal summaries.


The numerator associated with describing influenza activity depends on each surveillance component. Therefore, numerator data may include the number of ILI visits, laboratory-confirmed cases, influenza-associated hospitalizations, pneumonia and influenza deaths, or student absences, depending on the surveillance component presented. For seasonal influenza data collected by the Utah Department of Health, please visit [].


The denominator associated with describing influenza activity depends on the surveillance component being presented.

Healthy People Objective IID-22:

Increase the number of public health laboratories monitoring influenza virus resistance to antiviral agents
U.S. Target: 25 public health laboratories

How Are We Doing?

The Utah Department of Health Surveillance Program is always improving influenza data analysis and dissemination of results. Improvement of influenza surveillance systems can help identify high-risk groups, and ensure appropriate vaccine recommendations for all Utah residents.

How Do We Compare With the U.S.?

Direct comparison between the U.S. and Utah for influenza disease morbidity is difficult to conduct due to the variety of methods used to conduct surveillance. Counts of influenza-related hospitalizations now occur during a given influenza season in Utah; however, this condition has not been reportable at the national level, so reliable estimates and thus comparisons do not exist. A more reasonable way to compare Utah with the U.S. is to use the major descriptors of an influenza season (i.e. season peak, circulating types, general morbidity). Utah has mimicked national influenza trends the majority of the time during the past several seasons. During the 2009 H1N1 influenza pandemic, Utah was one of the hardest hit states during the spring wave of the pandemic (spring and early summer of 2009). During the fall of 2009, even though Utah experienced an increase in H1N1 influenza activity, it was not as severe as compared to other states in the U.S.

What Is Being Done?

Influenza surveillance involves multiple components which work together to describe the magnitude and severity of a given influenza season. Surveillance data are provided to governmental decision-makers and the general public. Utah is always preparing for the possible occurrence of an influenza pandemic. This preparation includes evaluating current surveillance practices and assessing what can be improved upon to better measure how influenza is circulating in the community. Influenza surveillance is a complex system in Utah and adjustments and improvements are made each season. Influenza surveillance systems in Utah have improved due to the need that existed during the 2009 H1N1 pandemic to better track the H1N1 influenza virus. Surveillance for influenza in Utah includes, but is not limited to the following: * tracking hospitalized cases of influenza, * tracking student absenteeism in schools, and * tracking pneumonia and influenza-associated deaths. [[br]] A weekly influenza surveillance report is posted to the Utah Department of Health -- Bureau of Epidemiology website ([]) each Wednesday during the influenza season (October through May). There are several ways to prevent influenza. The main way to keep from getting sick is to get a yearly influenza (flu) vaccine. It is recommended that a person get a flu vaccine every year because circulating viruses change. In 2003, the Food and Drug Administration (FDA) approved a nasal spray influenza vaccine called FluMist. The FDA approved FluMist for use in healthy people aged 2 to 49 years. Individuals wanting to receive influenza vaccine can contact their health care provider, a pharmacy, or their local health department. To use this tool go to: []. The Utah Department of Health works to ensure enough vaccine is provided for those who need to receive it each and every season. This involves making sure the amount of vaccine the state receives is enough to meet demand and to make sure that the flu vaccine is distributed where it is needed, such as local health departments. Current recommendations from the Advisory Committee on Immunization Practices (ACIP) is that everyone 6 months and older get the flu shot. This recommendation is different than previous recommendations that targeted specific groups (elderly, immune compromised etc.). If you do get influenza, antiviral medicines prescribed by your health care provider can reduce the length of time you are ill. To be effective, antiviral medicines must be taken within 48 hours after symptoms begin.

Available Services

The 2015-2016 influenza vaccine was developed for distribution starting September 2015.
Page Content Updated On 10/07/2015, Published on 11/09/2015
The information provided above is from the Department of Health's Center for Health Data IBIS-PH web site ( The information published on this website may be reproduced without permission. Please use the following citation: " Retrieved Mon, 26 September 2022 12:31:32 from Department of Health, Center for Health Data, Indicator-Based Information System for Public Health Web site: ".

Content updated: Thu, 20 Jun 2019 13:03:28 MDT