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Types of Flu: Learn the ABCs

  • What it means to have “the flu”

    What it means to have “the flu”

    Fever, cough, sore throat, and chills — these are
    all common symptoms of flu, or influenza. According to the National Institute of Allergy and Infectious Diseases
    (NIAID), millions of Americans suffer from such symptoms
    every flu season.

    Although people often say they have “the flu,” there
    are actually several kinds of viruses that can cause respiratory illness. In
    addition to true influenza, other non-influenza viruses can also cause flu-like
    illnesses. Understanding the different types of flu can help you better prepare
    for flu season.

  • The ABC’s of flu

    The ABC’s of flu

    Flu viruses are classified into three groups: A, B
    and C. Influenza A and B are the most common types of viruses. These strains
    cause the annual seasonal flu. They’re also responsible for occasional
    pandemics linked to new strains and subtypes. Influenza A viruses have subtypes
    H and N based on differences in surface proteins. Unlike B viruses that only
    infect humans, A strains can cross between species.

    Influenza C is not as common as A and B strains. It
    isn’t related to the seasonal flu or large scale outbreaks. Symptoms of
    influenza C are much more mild. The annual flu vaccine doesn’t offer protection
    against C viruses.

  • Evolution of a flu virus

    Evolution of a flu virus

    In addition to flu classifications, it’s also
    important to understand how new viruses form. Each type of flu evolves based on
    genetic changes. This explains how some viruses can start in animals and
    eventually end up causing illness in humans.

    Many influenza A viruses start in birds and then directly
    make their way to humans. Sometimes the virus goes through pigs as well.
    Influenza A subtypes from different species can also mix together to form new
    and different viruses. 

  • Seasonal flu viruses

    Seasonal flu viruses

    Influenza A and B are responsible for the miserable
    flu symptoms many Americans experience every fall and winter, including:

    • fever and chills
    • body aches, headache, and sore throat
    • cough and wheezing
    • excessive fatigue

    Symptoms typically last for one to two weeks, unless
    other complications develop.

    Seasonal flu viruses are highly contagious and
    mostly spread through small droplets in the air from infected persons. You can
    also contract influenza from touching infected surfaces and then touching your
    mouth, nose, or eyes. This is why regular hand washing is especially important
    during flu season.

    According to the U.S. Centers for Disease Control
    and Prevention (CDC), a person is typically contagious one day
    before symptoms start and up to 5 to 7 days after.

  • Swine flu (H1N1)

    Swine flu (H1N1)

    Technically known as H1N1, this is a type of
    Influenza A virus. Known as “swine flu,” the strain was new to humans in 2009.
    It was dubbed swine flu because the virus was originally exclusive to pigs.
    Symptoms of H1N1 are the same as the seasonal flu.

    The virus caused a pandemic between 2009 and 2010.
    That’s because at that time humans had no immunity against it. Since then,
    every seasonal flu shot offers protection against H1N1.

  • Avian influenza viruses

    Avian influenza viruses

    More commonly known as the “bird flu,” the avian
    influenza virus is an A virus that starts in birds. One example is the H5N1 subtype.
    This virus has caused numerous poultry deaths in the Middle East and Asia over
    the last decade. reports that although this same
    strain doesn’t typically infect people, it has been responsible for at least
    600 human cases since 2003. The strain is believed to be transmitted from birds
    and poultry to humans but not between people. They are no documented cases of
    this virus in the United States.

    H7N9 is another form of avian flu virus. According
    to, no cases of H7N9 have been found
    in birds or humans in the U.S. Still, given the way flu viruses transform, it
    shouldn’t be ignored. It has caused severe respiratory infections and some deaths
    in China.

  • Flu pandemics

    Flu pandemics

    Flu pandemics are related to influenza A viruses
    that are newly introduced to the human population. Flu shots may offer immunity
    to known virus strains, but they can’t protect against unknown strains. This lag
    in lack of protection can leave humans vulnerable. The pandemic of the HINI
    swine flu that started in 2009 is a good example.

    Despite the severity of pandemics, they’re a rare
    occurrence. documents a total of three
    pandemics of Influenza A that occurred during the 20th century. The best way to
    prepare and protect yourself during any flu season is to get vaccinated, and
    limit your travel and your exposure to large crowds. Equally important is to practice
    good hygiene habits, especially regular hand washing.

  • Constant changes to flu viruses

    Constant changes to flu viruses

    Scientists and health professionals both rely on the
    influenza classification process to name and diagnose new strains of flu. But
    flu viruses constantly change.

    This phenomenon is referred to as an antigenic
    drift. New viruses form over time, which is why the annual influenza vaccine
    contains different strains from year to year.

    No matter what types of viruses develop over time,
    you can help protect yourself and others by practicing good hygiene. This
    includes regular hand washing and covering your nose and mouth when you sneeze.
    Getting an annual flu shot is also very important to keeping yourself healthy.

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  • About pandemics. (n.d.). Retrieved from [3]
  • About the flu. (n.d.). Retrieved from [4]
  • Avian influenza A (H7N9) Virus. (n.d.). Retrieved from [5]
  • H5N1 avian flu – H5N1 bird flu. (n.d.). Retrieved from [6]
  • Influenza. (n.d). Retrieved from [7]
  • Influenza (flu) viruses. (2014, May 19). Retrieved from [2]

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Posted by: Dr.Health

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