Flu Season 2009-10

This spring, a new influenza virus began causing illness in people and spreading around the world. Originally called "swine flu" because the virus genes were similar to some influenza viruses that infect pigs, the new virus has been named "novel H1N1." Find out more about novel H1N1 and CDC's public health response.

Flu seasons are unpredictable in a number of ways. Although epidemics of flu happen every year, the timing of the flu season and its severity depend on many factors, including what influenza viruses are circulating and how well viruses in the vaccine match circulating influenza viruses. From September through early December, influenza activity remained low in the United States. Activity increased from early December through the end of the year and has continued to increase in January and February. By the week ending February 16, 2008, 49 states were reporting widespread influenza activity.

CDC's Influenza Division collects, compiles and analyzes information on influenza activity in the United States each week from October through May. New surveillance information is posted weekly at: Flu Activity & Surveillance.

What recommendations are CDC making about flu this season?
How much flu vaccine will be available in the United States this season?
Who should get vaccinated?
The Flu and Bacterial co-infections
Flu Season Characteristics

For information on Avian Flu

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What recommendations are CDC making about flu this season?

To reduce the substantial burden of influenza on the U.S., CDC recommends a three-pronged approach:

1. Vaccinate: Take time to get a vaccine.
   1. A flu vaccine is the best way to protect against the flu.
   2. The flu vaccine protects against three different flu viruses.
   3. Getting a vaccine is very important for people at high risk for serious flu complications and their close contacts. People at high risk include infants, pregnant women, people with chronic health conditions like asthma, diabetes or heart disease, and people 65 and older.
   4. This year, an all-time high supply of vaccine is available so more people than ever can seek protection from the flu.
   5. Because flu season can last as late as May, getting a flu vaccine late in the the season can still be beneficial.

2. Stop Germs: Take everyday preventive actions.
   1. Cover your nose and mouth with a tissue when you cough or sneeze-throw the tissue away after you use it.
   2. Wash your hands often with soap and water, especially after you cough or sneeze. If you are not near water, use an alcohol-based hand cleaner.
   3. Stay away as much as you can from people who are sick.
   4. If you get the flu, stay home from work or school. If you are sick, do not go near other people so that you don't make them sick.
   5. Try not to touch your eyes, nose, or mouth. Germs often spread this way.

3. Antiviral Drugs: Take antiviral drugs if your doctor says you need them.
   1. There are flu antiviral drugs that can treat the flu or prevent infection with flu viruses.
   2. For treatment, antiviral drugs should be started within 48 hours of getting sick.
   3. For prevention, antiviral drugs are 70% to 90% effective in preventing infection.
   4. These drugs must be prescribed by a health care provider.
   5. If you develop flu-like symptoms (usually high fever, headache, extreme tiredness, dry cough, sore throat, runny or stuffy nose and muscle aches), or are exposed to the flu before you get a flu vaccine, your health care professional will decide whether you should take antiviral drugs.

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How much flu vaccine will be available in the United States this season?

This year, an all-time high supply of vaccine is available so more people than ever can seek protection from the flu. Total production of influenza vaccine for the United States is anticipated to be 100 million doses for the 2007-08 season, depending on demand and production yields. However, influenza vaccine distribution delays or vaccine shortages remain possible in part because of the inherent critical time constraints in manufacturing the vaccine given the annual updating of the influenza vaccine strains and various other manufacturing and regulatory issues.

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Who should get vaccinated?

In general, anyone who wants to reduce their chances of getting the flu can get vaccinated. However, it is recommended by ACIP that certain people should get vaccinated each year. They are either people who are at high risk of having serious flu complications or people who live with or care for those at high risk for serious complications. During flu seasons when vaccine supplies are limited or delayed, ACIP makes recommendations regarding priority groups for vaccination.

People who should get vaccinated each year are:

People at high risk for complications from the flu, including:

1. Children aged 6 months until their 5th birthday,
2. Pregnant women,
3. People 50 years of age and older, and
4. People of any age with certain chronic medical conditions;
5. People who live in nursing homes and other long term care facilities.

People who live with or care for those at high risk for complications from flu, including:

6. Household contacts of persons at high risk for complications from the flu (see above)
7. Household contacts and out of home caregivers of children less than 6 months of age (these children are too young to be vaccinated)
8. Healthcare workers.

Use of the Nasal Spray Flu Vaccine

It should be noted that vaccination with the nasal-spray flu vaccine is always an option for healthy* people 2-49 years of age who are not pregnant.

Who Should Not Be Vaccinated?

There are some people who should not be vaccinated without first consulting a physician. These include:

1. People who have a severe allergy to chicken eggs.
2. People who have had a severe reaction to an influenza vaccination in the past.
3. People who developed Guillain-Barré syndrome (GBS) within 6 weeks of getting an influenza vaccine previously.
4. Influenza vaccine is not approved for use in children less than 6 months of age.
5. People who have a moderate or severe illness with a fever should wait to get vaccinated until their symptoms lessen.

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What can we expect this season in terms of bacterial co-infections, including Staphylococcus aureus, with flu?

Bacterial infections can occur as co-infections with influenza or occur following influenza infection. Last year, CDC noted an increase in flu and Staphylococcus aureus (S. aureus) co-infections among children who had died or were hospitalized with influenza infection. Some of those infections were with methicillin-resistant S. aureus (MRSA). CDC is working with state and local public health authorities to monitor and investigate flu-S. aureus co-infections, including pneumonias and other types of S. aureus infections. On January 30, 2008 CDC issued a Health Advisory on Influenza-Associated Pediatric Mortality and Staphylococcus aureus co-infection. For more information about flu and staph infections visit Seasonal Flu and Staph Infection.

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Flu Season Characteristics

What sort of flu season is expected this year?
Influenza (flu) seasons are unpredictable. Although epidemics of flu happen in most years, the beginning, severity, and length of the epidemic can vary widely from year to year. Before a season begins, it is not possible to accurately predict the features of any season.

Will new strains of influenza virus circulate this season?
Influenza viruses are constantly changing, so it's not unusual for new strains of influenza virus to emerge at any time of the year. For more information about how influenza viruses change, visit How the Flu Virus Can Change - "Drift" and "Shift".

Will this season's vaccine be a good match for circulating influenza viruses?
Most of the influenza viruses that have been isolated so far in the United States are well matched to the strains contained in this year's vaccine. For the most current CDC information regarding influenza viruses circulating in the United States, please refer to the CDC Weekly Surveillance Report.

For more information:

• Flu Basics
• Pandemic Flu Planning
• Weekly US Map: Influenza Summary Update
• CDC: Flu Information for Specific Groups
• USACHPPM: Influenza Resources
• National Institute of Allergy and Infectious Diseases: Flu Fact Sheets