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Honors ~ Influenza 1011
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Honors ~ Influenza 1011

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Honors ~ Influenza 1011 Honors ~ Influenza 1011 Presentation Transcript

  • Influenza
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  • What is a ‘type’ or strain?
    • Refers to genes and mechanisms/structures
      • Type A
      • Type B
      • H
      • N
  • vRNA
    • Type A = 8 viral RNA (vRNA) = 13.5 kb
      • vRNA is copied by viral RNA polymerase coded within, forming complementary RNA (cRNA)
      • cRNA can be translated into viral proteins
      • cRNA replicated into vRNA
  • H/HA = hemagglutinin
    • Responsible for virus entering host cells.
  • N/NA = neuraminidase
    • Responsible for new viruses leaving host cell.
  • Neuraminidase inhibitor
    • Cause budding virus to aggregate at cell surface; active against A & B
  • Influenza Evolution
  • Influenza Evolution
    • Very high rate of mutation; 1 in 1000 bases may change per single case of influenza.
    • Infection involves multiple replication cycles.
    • Accumulated mutations = genetic drift .
    • Antigenic shift : DNA mutations change viral proteins that are target of immune systems.
  • Genetic Shift - Reassortment
    • When animal simultaneously by several strains of virus.
    • Random gene packaging.
    • Often in swine
    • Start of all major pandemics
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  • Influenza Genome
    • Used by public health officials like bar code to monitor spread and evolution of influenza.
    • Virus emerges in one country and spreads to another can be identified by similarity of gene sequence.
    • Virus that spreads from one species to another will retain similar genomic sequence.
    • New virus genome which emerges through reassortment will NOT match previously isolated strains (parts might match, but not whole).
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  • Pandemics
  • Spanish Flu (1918–1920)
    • Category 5
    • H1N1
    • "the greatest medical holocaust in history"
    • As many as 25 million may have been killed in the first 25 weeks;
    • in contrast,  HIV/AIDS  has killed 25 million in its first 25 years
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  • 2009 Flu Pandemic (2009-2010)
    • Mexico in March–April 2009
    • H1N1 influenza
    • Commonly referred to as swine flu.
    • WHO: first influenza pandemic of the 21st century
    • Reassortment of four known strains of influenza A virus subtype H1N1:
      • one endemic in humans
      • one endemic in birds
      • two endemic in pigs (swine)
    • 199 countries and overseas territories/communities have officially reported a total of over 482,300 laboratory confirmed cases of the influenza pandemic H1N1 infection, that included 6,071 deaths
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  • H5N1
    • Common: Bird Flu or Avian Flu
    • endemic in many bird populations, especially in Southeast Asia
    • killing tens of millions of birds and spurring the culling of hundreds of millions of others.
    • no evidence of efficient human-to-human transmission
    • 60% mortality rate
    • world's largest current pandemic threat
    • billions of dollars are being spent researching H5N1 and preparing for a potential influenza pandemic
    • only a few antigenic shift mutations or antigenic drift mutations from being an avian influenza virus to being a human flu virus
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  • NCBI Flu Database
  • Your Hypothesis
    • State a hypothesis that can be tested by visualizing the genetic between different strains of virus.
    • Example : Due to geographical proximity of China and Hong Kong, the H5N1viral strains circulated in the period of 2000-2005 in birds should be similar in both places.