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SWINE FLU

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					H1N1: “Swine Flu”
      Why you should care…
• Every year between 5 and 20% of the
  population gets the flu.
• The CDC estimates that the flu kills
  36,000 people annually.
• On average over 200,000 people are
  hospitalized for flu related infections.
• The Flu season is from November to
  March
               Who gets it?
• Animals and humans




• Pigs, birds, and humans are the preferred hosts,
  and each have their own strain (type) of influenza
  that has unique characteristics from other strains.
               Who gets it?
• Since pigs, birds, and humans are the preferred
  hosts, interactions among these species allow
  host-adapted strains (virus changes to live in or
  benefit from unique characteristics of cell of its
  different hosts) that can be identified by serotype
  (like H1N1).
        Types of Influenza
• There are two main types:
  – Influenza A
  – Influenza B
• Each type (A & B) has subtypes
• Flu viruses are always changing to
  different subtypes
 Serotype of the strain is the “H”
  and “N” of its name, “H1N1”
                                                                   HA
• HA = hemagglutinin (16 types)
                                                   (Binds to
   – Allows the virus to bind to host cells.       receptors
                                                   on host cell)

   – Hijacks host receptor to gain entry.
• NA = neuraminidase (9 types)
   – Allows the virus to escape host cells so it
     can spread to other cells.
• M2 = protein important for virus
  replication.
• Different combinations of H and N                           NA
                                                           (Helps initiate

  determine which species are                              infection)


  susceptible and the morbidity of the
  infection.
H1N1: Let’s Take a Look
                      HA


(Binds to receptors
on host cell)




              NA
          (Helps initiate
          infection)
 How does the Flu Virus Change?
– The Flu Virus is ALWAYS changing
– Antigenic Drift – small changes that happen
  continually over time
   • Happens often
   • LESS DRAMATIC CHANGE
– Antigenic Shift – abrupt, major change in the
  influenza A virus, resulting in a new subtype
   • Happens less often
   • MUCH MORE DRAMATIC CHANGE
     The Evolution of Influenza Viruses
                  Antigenic drift




  “A” immune       “B” susceptible   “A” susceptible

                  Antigenic shift




Mixed infection     Reassortment      New strain of virus
  Why do we get the flu over and over?
Influenza viruses can change in
    several ways:
• It is an RNA virus so it
    doesn’t have the same
    “spell check” mechanism
    that DNA viruses do.
    Influenza can mutate all by
    itself through errors in
    replication without
    correction.
• Influenza also switches
    genes with other strains
    that code for surface
    proteins.
    – This is common during
      “mixed infections” where a
      cell is infected with more
      than one strain.
Why do we get the flu over and over?
• The immune system
  does not recognize the
  new, host-adapted
  strains.
• Pig cells are like mixing
  pots. They are
  susceptible to influenza
  usually found in pigs,
  humans, and birds!
   – Their cells have
     receptors for human
     and bird viruses as
     well as pig viruses
       Pandemic = PANIC?
• This is a new strain of influenza (H1N1)
  and most people are going to be
  susceptible; HOWEVER, it is not a strain
  with a high mortality.
• We are not all going to die.
• The WHO scaled up this virus to a phase 5
  pandemic based on distribution and
  human-human transmission, not based
  on lethality.
Prevention and Preventing Spread
• Get vaccinated!
• Cover your nose and mouth when you
  cough or sneeze.
• Wash your hands often especially after
  coughing or sneezing.
• Avoid close contact with sick people.
Avoid close contact with sick pigs.
         Questions?

				
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posted:9/10/2012
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