Influenza Fact Sheet

  • Influenza and pneumonia combined are the eighth leading cause of death among all Americans and the seventh leading cause of death among all Americans over the age of 65.1 Influenza and pneumonia together resulted in 56,326 deaths in 2006.2
  • In 2005 influenza and pneumonia represented a cost of $40.2 billion to the U.S. economy, $6.0 billion due to indirect costs and $34.2 billion in direct costs.3
  • For healthy children and adults, influenza is typically a moderately severe illness. For unhealthy or elderly people, influenza can be very dangerous.4
  • During the 2007–2008 influenza season, deaths associated with influenza and pneumonia peaked at 9.1% per week. The proportion of deaths associated with influenza and pneumonia were above the epidemic threshold for 13 consecutive weeks beginning in January 2008.5
  • Adults 65 years of age and older who contract seasonal influenza are much more likely to have serious complications from this illness, which can affect their health and independence.6
  • A person can have influenza more than once because there are different families and strains of the virus, each of which can lead to a new infection. Influenza A strains tend to cause more severe illness than B strains. Both are responsible for the seasonal influenza outbreaks that occur each fall and winter. Influenza C strains cause only mild respiratory illness and do not cause community outbreaks.7
  • Novel H1N1 is a subtype of the A strain. The novel H1N1 influenza virus that emerged in April 2009 is a mix of swine, human and avian influenza virus genes.8 It is a new strain within the influenza A family to which people have a low resistance, particularly those under 24 years of age. Transmission has continued around the world and may increase in the Northern Hemisphere during fall and winter (flu season). A vaccination against novel H1N1 is currently being developed and is expected to be available by mid-October 2009.9
  • Avian influenza, or bird flu, is a subtype of the A strain virus. While highly contagious in birds, it does not usually infect humans. Several cases of human infection with bird flu viruses have occurred since 1997, primarily in Asia, parts of Europe, the Near East and Africa. The virus is mainly transmitted to humans by direct contact with infected live, sick or dead poultry. However, it is thought that a few cases of human-to-human spread have occurred.10 The death rate for these reported cases has been approximately 60 percent.11
  • Some of the symptoms associated with influenza are:12
    • fever
    • dry cough
    • sore throat
    • headache
    • extreme tiredness
    • runny or stuffy nose
    • muscle aches
  • SARS, a potentially more serious illness, may start like the flu. Check with your health care provider immediately if complications such as difficulty breathing occur in areas where SARS is found.
  • Influenza is a very serious illness for anyone at high risk. Certain diseases that place people at high risk include:13
    • chronic lung disease such as asthma, emphysema, chronic bronchitis, bronchiectasis, or cystic fibrosis
    • heart disease
    • chronic kidney disease
    • diabetes or other chronic metabolic disorder
    • severe anemia
    • diseases or treatments that suppress immunity
  • Annual seasonal flu shots are recommended for all persons, including school-aged children, who want to reduce the risk of becoming ill with influenza or of transmitting influenza to others. In addition, the following groups are encouraged to get annual influenza vaccinations:14
    • children aged 6 months through 18 years;
    • people aged 50 years and older;
    • adults and children with chronic medical conditions;
    • children and adolescents who are receiving long-term aspirin therapy;
    • adults and children with suppressed immune systems caused by either medications or human immunodeficiency virus [HIV]);
    • adults and children who have any condition (e.g., cognitive dysfunction, spinal cord injuries, seizure disorders, or other neuromuscular disorders) that can compromise respiratory function or the handling of respiratory secretions or that can increase the risk for aspiration;
    • healthcare workers,
    • household contacts and caregivers of children and adults at high risk for influenza complications, with particular emphasis on vaccinating contacts of children aged <6 months.
    • residents of nursing home and other chronic- or long-term care facilities;
    • women who will be pregnant during the influenza season.
  • According to an American Lung Association study, the flu shot is safe for people with asthma.15 In 2007 46.1% of adults with asthma received the flu shot.16
  • In 2007, 72.0% U.S. adults age 65 and older received the flu shot during the preceding year.17
  • Influenza shots are covered by Medicare and other health insurance programs.18
  • Most people experience little or no reaction to the flu shot. The most common side effect is soreness where the vaccination is given for less than two days, which affects 10 to 64 percent of adult patients.19
  • The newest option for vaccination against seasonal flu is FluMist. FluMist is the first nasal spray vaccine for influenza and has been approved by the FDA for healthy people ages 2 through 49 years of age. Safety has not been shown in high-risk groups.20
  • The best period to receive either of the seasonal influenza vaccines is soon after the vaccine becomes available in the fall of each year. After receiving the flu shot it takes about two weeks for the body to develop immunity to influenza. It is not too late to get the vaccine in February or March since influenza activity may not peak until this time.21
  • Antiviral drugs can be useful for treating influenza A and/or B if given within 48 hours or less of the onset of influenza. These drugs may be used as preventive medications, but they must be taken daily as long as influenza cases continue to occur in the community. They may cause mild side effects. CDC recommendations for the use of antivirals in regards to influenza are being revised to account for resistance to the medicines among circulating influenza strains and the emergence of novel H1N1 influenza.22 Until these are published, interim guidelines are available here.

For more information on influenza, you can review the Influenza (Flu) Center, the Trends in Pneumonia and Influenza Morbidity and Mortality Report, other Epidemiology and Statistics Reports, or call the American Lung Association at 1-800-LUNG-USA (1-800-586-4872).

Sources:

1. Centers for Disease Control and Prevention. National Center for Health Statistics. Web-based Injury Statistics Query and Reporting System (WISQARS) 2006. Accessed on August 26, 2009.

2. Centers for Disease Control and Prevention. National Center for Health Statistics. National Vital Statistics Reports. Deaths: Final Data for 2006. April 17, 2009; 57(14).

3. Unpublished data from the National Heart, Lung, and Blood Institute, 2007 provided upon special request.

4. Centers for Disease Control and Prevention. Prevention and Control of Influenza: Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2009. Morbidity and Mortality Weekly Report. July 31, 2009; 58(RR-08).

5. Centers for Disease Control and Prevention. Update: Influenza Activity – United States – September 30, 2007–April 5, 2008, and Composition of the 2008-09 Influenza Vaccine. Morbidity and Mortality Weekly Report. April 2008; 57(15);404-409.

6. Centers for Disease Control and Prevention. Prevention and Control of Influenza: Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2009. Morbidity and Mortality Weekly Report. July 31, 2009; 58(RR-08).

7. Australian Government Department of Health and Aging. Pandemic Influenza. Avian Influenza (Bird Flu) – key facts. September 3, 2009. Available at http://www.flupandemic.gov.au/internet/panflu/publishing.nsf/Content/avian-influenza-key-facts-1. Accessed on September 2, 2009.

8. Centers for Disease Control and Prevention. Novel H1N1 Flu (Swine Flu) and You. August 5, 2009. Available at http://www.cdc.gov/h1n1flu/qa.htm. Accessed on September 2, 2009.

9. Centers for Disease Control and Prevention. Use of Influenza A (H1N1) 2009 Monovalent Vaccine: Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2009. Morbidity and Mortality Weekly Report August 21, 2009;58[Early Release]:1-8.

10. Centers for Disease Control and Prevention. Key Facts About Avian Influenza (Bird Flu) and Avian Influenza A (H5N1) Virus. May 7, 2007. Available at http://www.cdc.gov/flu/avian/gen-info/facts.htm.  Accessed on September 2, 2009.

11. Centers for Disease Control and Prevention. Avian Influenza (Bird Flu), What You Should Know, Current Situation. October 27, 2008. Available at http://www.cdc.gov/flu/avian/outbreaks/current.htm. Accessed on September 2, 2009.

12. Centers for Disease Control and Prevention. Seasonal Flu. Flu Symptoms and Severity. March 13, 2009. Available at http://www.cdc.gov/flu/about/disease/symptoms.htm. Accessed on September 2, 2009.

13. Centers for Disease Control and Prevention. Prevention and Control of Influenza: Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2009. Morbidity and Mortality Weekly Report. July 31, 2009; 58(RR-08).

14. Ibid.

15. The American Lung Association Asthma Clinical Research Centers. The Safety of Inactivated Influenza Vaccine in Adults and Children with Asthma. New England Journal Medicine.  Vol. 345; 1529-36: November 2001.

16. Centers for Disease Control and Prevention. Behavioral Risk Factor Surveillance System, 2007 raw data. Analysis by the American Lung Association, Research and Program Services Division.

17. Centers for Disease Control and Prevention. Behavioral Risk Factor Surveillance System, Prevalence Report 1997-2007. Available at http://apps.nccd.cdc.gov/brfss/. Accessed on September 11, 2008.

18. Centers for Disease Control and Prevention. Prevention and Control of Influenza: Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2009. Morbidity and Mortality Weekly Report. July 31, 2009; 58(RR-08).

19. Ibid.

20. Ibid.

21. Ibid.

22. Ibid.