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 - Northwestern Memorial Hospital - Chicago

Common questions about influenza

What is influenza (also called flu)?

The flu is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness, and at times it can lead to death.

How does the flu spread?

Predominant medical theory suggests that flu viruses spread from person-to-person when people with influenza cough or sneeze. Additionally, people may also become infected by touching something with flu viruses on it and then touching their mouth, nose or eyes. It is generally thought that most healthy adults can infect others beginning 1 day before symptoms develop and up to 5 to 7 days after becoming sick. That means that 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.

What’s the best way to prevent the flu?

The single best way to prevent seasonal flu is to get a seasonal flu vaccination each year. For the 2010–2011 flu season, there is only one flu vaccine being offered. H1N1 is included in this season's vaccine, so there is no need to receive two vaccinations.

How can I get vaccinated?

Vaccinations come in two prevalent forms: the flu shot and the nasal spray flu vaccine.

  • The "flu shot" is an inactivated vaccine containing killed flu virus that is given with a needle. The seasonal flu shot is approved for use in people 6 months of age and older, including healthy people and people with chronic medical conditions. The vaccine cannot cause the flu.

  • The nasal-spray flu vaccine is 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 2 to 49 years of age who are not pregnant. About 2 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.

When is the best time to get vaccinated against seasonal flu?

Because the timing and duration of flu seasons vary, yearly seasonal flu vaccination should begin in September, or as soon as the seasonal flu vaccine is available. Vaccinations can and should continue throughout the flu season into December, January and beyond. While seasonal flu outbreaks can happen as early as October, most of the time seasonal flu activity peaks in January or later.

Who should get vaccinated against seasonal flu?

In general, anyone who wants to reduce their chances of getting seasonal flu can get vaccinated. However, certain people should get vaccinated each year either because they are at high risk of having serious flu-related complications or because they live with or care for high-risk persons. During flu seasons when vaccine supplies are limited or delayed, the Advisory Committee on Immunization Practices (ACIP) makes recommendations regarding priority groups for vaccination.

People who should get a seasonal flu vaccination each year include

  1. Children aged 6 months up to their 19th birthday
  2. Pregnant women
  3. People 50 years of age and older
  4. People of any age with certain chronic medical conditions
  5. People who live in nursing homes and other long-term care facilities
  6. People who live with or care for those at high risk for complications from flu, including:
    • Healthcare workers
    • Household contacts of persons at high risk for complications from the flu
    • Household contacts and out-of-home caregivers of children under the age of 6 months (these children are too young to be vaccinated)

Are there people who should not be vaccinated for the flu?

Some people should not be vaccinated without first consulting a physician. They include:

  • People who have a severe allergy to chicken eggs
  • People who have had a severe reaction to an influenza vaccination in the past
  • People who developed Guillian-Barré Syndrome (GBS) within 6 weeks of getting an influenza vaccine previously
  • Children under the age of 6 months (influenza vaccine is not approved for use in this age group)

Note: People who have a moderate or severe illness with a fever should wait to get vaccinated until they are feeling better.

If you have questions about whether you should get a flu vaccine, consult your healthcare provider.

What should I do if I think or know I have the flu?

Good health habits, like covering your cough and washing your hands, often can help stop the spread of germs and prevent respiratory illnesses like the flu. There also are flu antiviral drugs that can be used to treat and prevent the flu. Always consult your doctor about what steps are necessary for you, but generally speaking, if you have flu-like symptoms, consider the following regimen:

Avoid close contact with others

Avoid close contact with people who are sick. When you are sick, keep your distance from others to protect them from getting sick too.

Stay home when you are sick

If possible, stay home from work, school, and errands when you are sick. You will help prevent others from catching your illness.

Cover your mouth and nose

Cover your mouth and nose with a tissue when coughing or sneezing. It may prevent those around you from getting sick.

Clean your hands

Washing your hands often will help protect you from germs.

Avoid touching your eyes, nose or mouth

Germs are often spread when a person touches something that is contaminated with germs and then touches his or her eyes, nose, or mouth.

Practice other good health habits

Get plenty of sleep, be physically active, manage your stress, drink plenty of fluids, and eat nutritious food. 

Last UpdateJune 9, 2011