What is influenza (also called flu)?
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.
Signs and symptoms of flu
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.
How flu spreads
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.
Period of contagiousness
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.
How serious is the flu?
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
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.
Preventing seasonal flu: Get vaccinated
The single best way to prevent the flu is to get a flu vaccine each season. There are two types of flu vaccines:
About two weeks after vaccination, antibodies develop that protect against influenza virus infection. Flu vaccines will not protect against flu-like illnesses caused by non-influenza viruses.
The seasonal flu vaccine protects against the three influenza viruses that research suggests will be most common.
When to get vaccinated against seasonal flu
Yearly flu vaccination should begin in September, or as soon as vaccine is available, and continue throughout the flu season which can last as late as May. This is because the timing and duration of flu seasons vary. While flu season can begin early as October, most of the time seasonal flu activity peaks in January, February or later.
Who should get vaccinated?
Everyone 6 months and older should get a flu vaccine each year. 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 U.S. to expand protection against the flu to more people. While everyone should get a flu vaccine each flu season, it’s especially important that certain people get vaccinated either because they are at high risk of having serious flu-related complications or because they live with or care for people at high risk for developing flu-related complications.
Who is at high risk for developing flu-related complications?
Who else should get vaccinated?
Other people for whom vaccination is especially important are: