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:
*It’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.
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), and persons who live in facilities like nursing homes.
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.
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 2013-2014 flu season.
Traditional flu vaccines made to protect against three different flu viruses (called “trivalent” vaccines) are available. In addition, this season flu vaccines made to protect against four different flu viruses (called “quadrivalent” vaccines) also are available.
The trivalent flu vaccine protects against two influenza A viruses 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:
(*”Healthy” indicates persons who do not have an underlying medical condition that predisposes them to influenza complications.)
CDC does not recommend one flu vaccine over the other. The important thing is to get a flu vaccine every year.
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.
Everyone who is at least 6 months of age should get a flu vaccine this season. This recommendation has been in place since February 24, 2010 when CDC’s Advisory Committee on Immunization Practices (ACIP) voted for “universal” flu vaccination in the United States to expand protection against the flu to more people.
While everyone should get a flu vaccine this season, it’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. People who have had a mild reaction to egg—that is, one which only involved hives—may receive a flu shot with additional precautions. Make sure your health care provider knows about any allergic reactions. Most, but not all, types of flu vaccine contain small amount of egg.
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).
Influenza vaccine is not approved for children younger than 6 months of age.
People who have had a severe allergic reaction to influenza vaccine should generally not be vaccinated.
There are some people who should not get a flu vaccine without first consulting a physician.