For most people, influenza, or flu, causes fever, coughing, headaches, aches and pains, and fatigue. Flu illness can escalate and develop into life-threatening complications like pneumonia and respiratory failure. Each year scientists predict which strains of the flu virus are likely to affect which areas of the world. Vaccines are developed and then distributed annually to help build immunity against seasonal flu viruses so as to protect against flu and its potentially serious complications.

A flu pandemic can occur when a novel, non-human strain of the flu virus emerges, and a given population has little or no immunity against it. If the virus spreads throughout a given population and then spreads across national or geographical boundaries, it becomes a global threat— a flu pandemic.

Flu pandemics have happened four times before in recent history—in 1918, 1957, 1968, and 2009. Governments, organizations, doctors, and scientists are working hard to plan for the next pandemic.

Health systems must be prepared for future pandemics before the pandemics occur, a key part of this is being able to distribute and administer vaccine effectively and efficiently. If people become ill, antivirals can treat flu infection, while antibiotics can treat secondary bacterial infections such as pneumonia. Health systems must be able to distribute and administer these treatments effectively. Pandemic preparedness plans are developed and implemented to reduce the impact of future pandemics.

For more information on flu or pandemics, please visit:

9,200,000 - 35,600,000

Cases of Influenza Yearly (United States)

140,000 - 710,000

Hospitalized for Influenza Yearly (United States)

12,000 - 56,000

Deaths from Influenza Yearly (United States)

Influenza News from the CDC

CDC International Influenza Updates

CDC Seasonal Flu Updates

  • Vaccine Effectiveness - How Well Does the Flu Vaccine Work?
    on October 12, 2018 at 9:25 pm

    CDC conducts studies each year to determine how well the influenza (flu) vaccine protects against flu illness. […]

  • Weekly U.S. Influenza Surveillance Report
    on October 12, 2018 at 3:00 pm

    During week 40 (Sept 30-Oct 6, 2018), flu activity is at levels below baseline in the U.S. […]

  • Seasonal Flu Shot: Questions & Answers
    on October 3, 2018 at 12:20 pm

    The flu shot is a vaccine given with a needle, usually in the arm. The seasonal flu shot protects against the three or four influenza viruses that research indicates will be most common during the season. […]

  • National Press Conference Kicks Off 2018-2019 Flu Vaccination Campaign
    on September 27, 2018 at 3:05 pm

    On September 27, 2018, the Centers for Disease Control and Prevention (CDC) and the National Foundation for Infectious Diseases (NFID) along with other public health and medical groups kicked off the 2018-2019 flu vaccine campaign at a press conference held at the National Press Club in Washington, D.C. […]

  • Misconceptions about Seasonal Flu and Flu Vaccines
    on September 25, 2018 at 3:00 pm

    CDC recommends use of any licensed, age-appropriate influenza vaccine (inactivated influenza vaccines [IIV], recombinant influenza vaccine [RIV], or live attenuated influenza vaccine [LAIV4]) with no preference expressed for one vaccine over another during the 2018-2019 flu season. […]

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