Flu Facts

What is the Flu

The flu is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness, and at times can lead to death. The best way to prevent the flu is to get a flu vaccine each fall when the vaccine is available.

Every year in the United States, on average:

  • 5% to 20% of the population gets the flu
  • More than 200,000 people are hospitalized from flu complications
  • Between 30,000-36,000 die from flu

Some people are at high risk for serious complications, such as older people, young children, and people with certain health conditions.

Symptoms and Complications of Flu

Symptoms of flu can include:

  • Dry cough
  • Extreme tiredness
  • Fever (usually high)
  • Headache
  • Muscle aches
  • Runny or stuffy nose
  • Sore throat
  • Gastrointestinal symptoms, such as nausea, vomiting, and diarrhea. These are much more common among children than adults.

Some of the complications caused by flu include bacterial pneumonia, dehydration, and worsening of chronic medical conditions, such as congestive heart failure, asthma, or diabetes. Children may get sinus problems and ear infections.

How Flu Spreads

The flu spreads in respiratory droplets caused by coughing and sneezing. It usually spreads from person to person, though occasionally a person may become infected by touching something with a virus on it and then touching their mouth or nose. Adults may be able to infect others beginning one day before getting symptoms and up to 7 days after getting sick. That means you can give someone the flu before you know you're sick, as well as while you are sick.

Flu Vaccines and Prevention

The single best way to prevent the flu is to get a flu vaccine each fall. About two weeks after vaccination, antibodies that provide protection against influenza virus infection develop in the body. There are two types of vaccines:

The flu shot is an inactivated vaccine (containing a killed virus) that is given with a needle. The flu shot is approved for use in people older than 6 months, including healthy people and people with chronic medical conditions.

The nasal spray flu vaccine, a vaccine made with live, weakened flu viruses that do not cause the flu (sometimes called LAIV for Live attenuated Influenza Vaccine). LAIV is approved for use in healthy people 5 years to 49 years of age who are not pregnant.

When to Get Vaccinated

October or November is the best time to get vaccinated, but you can still get vaccinated in December and later. Flu season can begin as early as October and last as late as May.

Who Should Get Vaccinated

Anyone who wants to reduce their chances of getting the flu can get vaccinated. However, certain people should get vaccinated each year either because they are at high risk of having serious flu complications or because they are in close contact with someone who is at high risk for serious complications and they could make them sick. People who should get vaccinated each year are:

  • People at high risk for complications from the flu
  • People 65 years and older
  • People who live in nursing homes and other long-term care facilities that house those with long-term illnesses
  • Adults and children 6 months and older with chronic heart or lung conditions, including asthma
  • Adults and children 6 months and older who needed regular medical care or were in a hospital during the previous year because of metabolic disease (like diabetes), chronic kidney disease, or weakened immune system (including immune system problems caused by medicines or by infection with human immunodeficiency virus (HIV/AIDS)
  • Children 6 months to 18 years of age who are on long-term aspiring therapy. (Children given aspirin while they have influenza are at risk of Reye syndrome.)
  • Women who will be pregnant during the influenza season
  • All children 6 to 23 months of age
  • People 50 to 64 years of age. (Nearly on-third of people 50 to 64 years of age in the United States have one or more medical conditions that place them at increased risk for serious complications from influenza)
  • People who can transmit influenza to others at high risk for complications. (This means that if you have contact with anyone in a high risk group (see you should get vaccinated. This includes health-care workers and parents or other close contacts of children 6 to 23 months, and close contacts of seniors.)

Who Should Not Be Vaccinated

There are some people who should not be vaccinated, including:

  • People who have a severe allergy to chicken eggs
  • People who have a severe reaction to influenza vaccination in the past
  • People who developed Guillain-Barre Syndrome (GBS) within 6 weeks of getting an influenza vaccine previously
  • Children less than 6 months of age
  • People who are sick with a fever (these people can get vaccinated once their symptoms lessen).