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:
People who live or work in crowded conditions (eg, nursing home, school, military, day care)
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.
Anyone who wants to reduce their risk of the flu should consider the vaccine. Those who should get a yearly flu vaccine include:
Children six months-18 years old
Parents, babysitters, and caretakers of children less than six months old (as these children are too young to be vaccinated)
Adults older than 50 years of age (shown to reduce hospitalizations and deaths in the elderly)
Those living or working in nursing homes and long-term care facilities
Those with chronic medical conditions
Those with chronic diseases, such as diabetes or
or conditions involving the kidneys, liver, lungs, heart, blood, or immune system
Women who are pregnant
Those living with someone who is at high risk for complications from the flu
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:
Less than nine years old and receiving influenza vaccine for the first time
Vaccinated last season for the first time, but with only one dose
What Are the Risks Associated With the Influenza Vaccine?
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:
Soreness, redness, and swelling around the injection site
Adverse effects associated with the nasal spray vaccine include:
Certain people should consult their doctor before receiving the influenza vaccine. These include:
People who have a severe allergy to chicken eggs
People who have had a severe reaction to a prior influenza vaccine
Children younger than six months
People who are sick with a fever
What Other Ways Can Influenza Be Prevented Besides Vaccination?
Good preventive measures include:
Avoid close contact with people who have respiratory infections.
Wash your hands often for 15-20 seconds with soap and water, especially when you come in contact with someone who is sick. Rubbing alcohol-based cleaners on your hands is also useful.
Do not share drinks or personal items.
Do not bite your nails or put your hands near your eyes, mouth, or nose.
What Happens in the Event of an Outbreak?
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,
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.
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.
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.
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