The flu is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and lungs. It can cause mild to severe illness, and at times can lead to death. The best way to prevent the flu is by getting a flu vaccine each year.
People who have the flu often feel some or all of these signs and symptoms:
*Itâ€™s important to note that not everyone with flu will have a fever.
Most experts believe that flu viruses spread mainly by droplets made when people with flu cough, sneeze or talk. These droplets can land in the mouths or noses of people who are nearby. Less often, a person might also get flu by touching a surface or object that has flu virus on it and then touching their own mouth, eyes or possibly their nose.Â\U00A0Top of Page
You may be able to pass on the flu to someone else before you know you are sick, as well as while you are sick. Most healthy adults may be able to infect others beginning 1 day before symptoms develop and up to 5 to 7 days after becoming sick. Some people, especially young children and people with weakened immune systems, might be able to infect others for an even longer time.
Flu is unpredictable and how severe it is can vary widely from one season to the next depending on many things, including:
Certain people are at greater risk for serious complications if they get the flu. This includes older people, young children, pregnant women and people with certain health conditions (such as asthma, diabetes, or heart disease).
Flu seasons are unpredictable and can be severe. Over a period of 30 years, between 1976 and 2006, estimates of flu-associated deaths in the United States range from a low of about 3,000 to a high of about 49,000 people.Â\U00A0Top of Page
Complications of flu can include bacterial pneumonia, ear infections, sinus infections, dehydration, and worsening of chronic medical conditions, such as congestive heart failure, asthma, or diabetes.
The single best way to prevent the flu is to get a flu vaccine each season.
There are several flu vaccine options for the 2014-2015 flu season.
Traditional flu vaccines made to protect against three different flu viruses (called â€œtrivalentâ€ vaccines) are available. In addition, flu vaccines made to protect against four different flu viruses (called â€œquadrivalentâ€ vaccines) also are available.
Trivalent flu vaccine protects against two influenza A viruses (an H1N1 and an H3N2) and an influenza B virus. The following trivalent flu vaccines are available:
The quadrivalent flu vaccine protects against two influenza A viruses and two influenza B viruses. The following quadrivalent flu vaccines are available:
(*â€œHealthyâ€ in this instance refers to children 2 years through 8 years old who do not have an underlying medical condition that predisposes them to influenza complications.)
Yearly flu vaccination should begin soon after flu vaccine is available, and ideally by October. However, getting vaccinated even later can be protective, as long as flu viruses are circulating. While seasonal influenza outbreaks can happen as early as October, most of the time influenza activity peaks in January or later. Since it takes about two weeks after vaccination for antibodies to develop in the body that protect against influenza virus infection, it is best that people get vaccinated so they are protected before influenza begins spreading in their community.
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Everyone 6 months of age and older should get a flu vaccine this season. This recommendation has been in place since February 24, 2010 when CDCâ€™s Advisory Committee on Immunization Practices (ACIP) voted for â€œuniversalâ€ flu vaccination in the United States to expand protection against the flu to more people.
While everyone 6 months and older should get a flu vaccine this season with rare exception, itâ€™s especially important for some people to get vaccinated.
Those people include the following:
More information is available at Who Should Get Vaccinated Against Influenza.
People who have ever had a severe allergic reaction to eggs may be advised not to get vaccinated or to get recombinant flu vaccine, if they are aged 18 through 49 years. People who have had a mild reaction to eggâ€”that is, one which only involved hivesâ€”may receive a flu shot with additional precautions. Recombinant flu vaccines also are an option for these people if they are aged 18 through 49 years and they do not have any contraindications to that vaccine. Make sure your doctor or health care professional knows about any allergic reactions. Most, but not all, types of flu vaccine contain a small amount of egg.
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Vaccination with the nasal-spray flu vaccine is an option for healthy* people 2 to 49 years of age who are not pregnant. Even people who live with or care for those in a high risk group (including health care workers) can get the nasal-spray flu vaccine as long as they are healthy themselves and are not pregnant. The one exception is health care workers who care for people with severely weakened immune systems who require a protected hospital environment; these people should get the inactivated flu vaccine (flu shot).
Starting in 2014-2015, CDC recommends use of the nasal spray vaccine (LAIV) in healthy children 2 through 8 years of age, when it is immediately available and if the child has no contraindications or precautions to that vaccine. Recent studies suggest that the nasal spray flu vaccine may work better than the flu shot in younger children. However, if the nasal spray vaccine is not immediately available and the flu shot is, children age 2 through 8 years old should get the flu shot. Donâ€™t delay vaccination to find the nasal spray flu vaccine. For more information about the new CDC recommendation, see Nasal Spray Flu Vaccine in Children 2 through 8 Years Old or the 2014-2015 MMWR Influenza Vaccine Recommendations.
Influenza vaccine is not approved for children younger than 6 months of age.
People who have had a severe allergic reaction to influenza vaccine or any of its components should generally not be vaccinated.
There are some people who should not get a flu vaccine without first consulting a physician.