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Flu Strains

Flu Information
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Influenza A is the flu strain responsible for major worldwide outbreaks, including the Spanish Flu Pandemic of 1918. Influenza A viruses can infect humans, domestic animals, and wild birds. Swine flu and Bird Flu are both subtypes of Influenza A.

Influenza B is the common flu and can appear at any time during the year. It is often the cause of outbreaks in communities, schools, and workplaces. Regular types A and B flu strains are included in each year’s seasonal flu vaccine.

Influenza C viruses cause mild respiratory illnesses but do not cause epidemics.

The seasonal flu vaccine does not include type C influenza strain. The 2009 H1N1 virus, sometimes referred to as the Swine Flu, is also not included in the regular flu vaccine. A separate vaccine was developed to protect against this new mutation of type A influenza.

Viruses constantly evolve in two different ways know as drift and shift. Drift is caused by small, gradual changes in the virus over time by mutation. This process produces new strains that may be unrecognizable by the body’s immune system. These changes in influenza viruses are monitored by the medical community to create flu vaccines for flu shots each year that protect against mutated strains.

Shift refers to abrupt major changes to Type A influenza that emerges from an animal population, which is radically different from existing subtypes in humans. These shifts occur, either by direct human-to-animal contact, or through the mixing of human and animal influenza A genes. These new subtypes are easily spread from person to person and can cause serious illness in humans. Shifts are blamed for past pandemics that include:

  • Spanish Flu -1918
  • Asian Flu - 1957
  • Hong Kong Flu - 1968
  • Swine Flu - 1976
  • Swine Flu - 2009

Symptoms are the same for different flu strains:

  • Fever
  • Fatigue
  • Body aches
  • Headache
  • Sore throat
  • Runny or stuffy nose
  • Cough
  • Nausea, vomiting, and/or diarrhea (mainly in children)

The flu can cause serious, life-threatening complications in small children, the elderly, and people with existing health problems. Complications may include pneumonia, bronchitis, sinus infections, and ear infections. People with asthma and heart problems may experience heightened symptoms of their existing conditions.

Yearly flu vaccination is the best way to prevent sickness from influenza, according to the CDC. Flu vaccines currently protect against influenza A (H1N1 and H3N2) and influenza B strains. Antiviral drugs may also be prescribed to prevent influenza, reduce the severity of symptoms, and shorten the duration of the illness. Antiviral drugs must be prescribed by a physician and taken within two days of becoming sick. They may also be given to a person who is not sick, but who may be at risk of contracting influenza.

There are four types of antiviral medicines approved for use in the United States against the common flu strains:

  • Oseltamivir (Tamiflu®) – Prescribed to treat and prevent influenza A and B in children over 1-year-of-age and adults.
  • Zanamivir (Relenza®) – Is used to treat influenza A and B in people 7-years and older, and to prevent A and B in children over 5-years-old and in adults.
  • Amantadine (Symmetrel®) – For treatment and prevention of influenza A in children over 1-year old and adults.
  • Rimantadine (Flumadine®) – Used to prevent influenza A in children over 1-year-of-age, and to treat people over 13-years-of-age.

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