• 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.

  Flu.gov 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 Flu.gov, 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. Flu.gov 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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References:

• About pandemics. (n.d.). Retrieved from http://www.flu.gov/pandemic/about/index.html [3]
• About the flu. (n.d.). Retrieved from http://www.flu.gov/about_the_flu/index.html# [4]
• Avian influenza A (H7N9) Virus. (n.d.). Retrieved from http://www.flu.gov/about_the_flu/h7n9/index.html [5]
• H5N1 avian flu – H5N1 bird flu. (n.d.). Retrieved from http://www.flu.gov/about_the_flu/h5n1/index.html [6]
• Influenza. (n.d). Retrieved from http://www.niaid.nih.gov/topics/flu/understandingflu/pages/definitionsoverview.aspx [7]
• Influenza (flu) viruses. (2014, May 19). Retrieved from
  http://www.cdc.gov/flu/about/viruses/ [2]

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