Seasonal influenza (also called the flu) is an upper respiratory infection. It is caused by the influenza virus. Flu strains differ from one year to the next. There are two main kinds infecting humans:
You can get the flu when you breathe in droplets from someone infected with the virus. It can also be spread by touching a contaminated surface and then putting your hand to your mouth or nose.
Each winter, the flu spreads around the world. Anyone can get it, but some are at greater risk than others:
On average, 5%-20% of the US population gets the flu each year. More than 200,000 people are hospitalized for flu-related complications. About 36,000 die from the disease.
Symptoms include:
Treatment may include:
There are two types of influenza vaccines:
The flu shot is approved for use in people older than six months. The shot is made from an inactivated, killed virus. It is given by injection, usually into the arm.
The nasal spray flu vaccine is approved for healthy people aged 2-49 years who are not pregnant. It is made from live, weakened flu viruses. It is taken by nasal spray.
Both vaccines contain three influenza viral strains—type A virus (H3N2), type A virus (H1N1), and a type B virus. The vaccine changes from year to year based on which viruses are likely to circulate in a given flu season.
(NOTE: The flu shot is not effective against pandemic H1N1 (2009) flu . You must get the vaccine for pandemic H1N1 (2009) flu. )
Anyone who wants to reduce their risk of the flu should consider the vaccine. Those who should get a yearly flu vaccine include:
It takes about two weeks for the vaccination to protect you against the flu. Even if you have been vaccinated, you can still get the flu. If you have symptoms, tell your doctor.
Flu season can begin as early as October and as late as April or May. The best time to get vaccinated is as soon as the vaccine becomes available. Doing so will protect you before the flu comes to your community.
It is recommended that two doses are given (separated by four weeks or more) to children who meet certain criteria:
Almost all people who receive the influenza vaccine have no problems. There are certain risks associated with the vaccine. As with any vaccine, there is a small risk of serious problems, including severe allergic reaction.
Adverse effects associated with the flu shot include:
Adverse effects associated with the nasal spray vaccine include:
Certain people should consult their doctor before receiving the influenza vaccine. These include:
Good preventive measures include:
In the event of an outbreak, vaccinating as many susceptible people as possible, especially those in priority groups, is the primary focus. In addition, the use of antiviral medications (eg, oseltamivir , zanamivir ) can reduce the duration of the illness when given within two days of onset. Certain antiviral medicines can also be given before exposure to Type A influenza virus to help prevent illness. Finally, people who are infected should be isolated as much as possible.
WHERE CAN I GET MORE INFORMATION?
Flu.gov
http://www.flu.gov/
National Immunization Program
Centers for Disease Control and Prevention
http://www.cdc.gov/vaccines/
Public Health Agency of Canada
http://www.phac-aspc.gc.ca/index-eng.php
Vaccines
US Food and Drug Administration
http://www.fda.gov/cber/vaccines.htm
References:
Asthma information for patients and parents of patients. Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/H1N1flu/asthma.htm. Updated September 15, 2009. Accessed September 15, 2009.
Flu. Centers for Disease Control and Prevention website. Available at:
http://www.cdc.gov/flu/keyfacts.htm. Accessed February 6, 2007.
Influenza vaccine in adults. DynaMed website. Available at: http://www.ebscohost.com/dynamed/what.php . Updated September 8, 2009. Accessed September 8, 2009.
Key facts about seasonal flu vaccine. Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/FLU/protect/keyfacts.htm. Updated December 10, 2008. Accessed September 1, 2009.
Vaccines and immunizations. Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/nip. Accessed February 6, 2007.
¹1/31/2008 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed/what.php: Centers for Disease Control and Prevention. Recommended immunization schedules for persons aged 0-18 years—United States, 2008. MMWR. 2008;57;Q1-Q4. Centers for Disease Control and Prevention, MMWR website. Available at: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5701a8.htm. Updated January 10, 2008. Accessed January 28, 2008.
²10/15/2007 DynaMed Systematic Literature Surveillance http://www.ebscohost.com/dynamed/what.php: Nichol KL, Nordin JD, Nelson DB, Mullooly JP, Hak E. Effectiveness of influenza vaccine in the community-dwelling elderly. N Engl J Med. 2007;357:1373-1381.
Last reviewed November 2009 by David L. Horn, MD, FACP
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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