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Honors ~ Influenza 1011


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Honors ~ Influenza 1011

  1. 1. Influenza
  2. 12. What is a ‘type’ or strain? <ul><li>Refers to genes and mechanisms/structures </li></ul><ul><ul><li>Type A </li></ul></ul><ul><ul><li>Type B </li></ul></ul><ul><ul><li>H </li></ul></ul><ul><ul><li>N </li></ul></ul>
  3. 13. vRNA <ul><li>Type A = 8 viral RNA (vRNA) = 13.5 kb </li></ul><ul><ul><li>vRNA is copied by viral RNA polymerase coded within, forming complementary RNA (cRNA) </li></ul></ul><ul><ul><li>cRNA can be translated into viral proteins </li></ul></ul><ul><ul><li>cRNA replicated into vRNA </li></ul></ul>
  4. 14. H/HA = hemagglutinin <ul><li>Responsible for virus entering host cells. </li></ul>
  5. 15. N/NA = neuraminidase <ul><li>Responsible for new viruses leaving host cell. </li></ul>
  6. 16. Neuraminidase inhibitor <ul><li>Cause budding virus to aggregate at cell surface; active against A & B </li></ul>
  7. 17. Influenza Evolution
  8. 18. Influenza Evolution <ul><li>Very high rate of mutation; 1 in 1000 bases may change per single case of influenza. </li></ul><ul><li>Infection involves multiple replication cycles. </li></ul><ul><li>Accumulated mutations = genetic drift . </li></ul><ul><li>Antigenic shift : DNA mutations change viral proteins that are target of immune systems. </li></ul>
  9. 19. Genetic Shift - Reassortment <ul><li>When animal simultaneously by several strains of virus. </li></ul><ul><li>Random gene packaging. </li></ul><ul><li>Often in swine </li></ul><ul><li>Start of all major pandemics </li></ul>
  10. 23. Influenza Genome <ul><li>Used by public health officials like bar code to monitor spread and evolution of influenza. </li></ul><ul><li>Virus emerges in one country and spreads to another can be identified by similarity of gene sequence. </li></ul><ul><li>Virus that spreads from one species to another will retain similar genomic sequence. </li></ul><ul><li>New virus genome which emerges through reassortment will NOT match previously isolated strains (parts might match, but not whole). </li></ul>
  11. 25. Pandemics
  12. 26. Spanish Flu (1918–1920) <ul><li>Category 5 </li></ul><ul><li>H1N1 </li></ul><ul><li>&quot;the greatest medical holocaust in history&quot; </li></ul><ul><li>As many as 25 million may have been killed in the first 25 weeks; </li></ul><ul><li>in contrast,  HIV/AIDS  has killed 25 million in its first 25 years </li></ul>
  13. 28. 2009 Flu Pandemic (2009-2010) <ul><li>Mexico in March–April 2009 </li></ul><ul><li>H1N1 influenza </li></ul><ul><li>Commonly referred to as swine flu. </li></ul><ul><li>WHO: first influenza pandemic of the 21st century </li></ul><ul><li>Reassortment of four known strains of influenza A virus subtype H1N1: </li></ul><ul><ul><li>one endemic in humans </li></ul></ul><ul><ul><li>one endemic in birds </li></ul></ul><ul><ul><li>two endemic in pigs (swine) </li></ul></ul><ul><li>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 </li></ul>
  14. 30. H5N1 <ul><li>Common: Bird Flu or Avian Flu </li></ul><ul><li>endemic in many bird populations, especially in Southeast Asia </li></ul><ul><li>killing tens of millions of birds and spurring the culling of hundreds of millions of others. </li></ul><ul><li>no evidence of efficient human-to-human transmission </li></ul><ul><li>60% mortality rate </li></ul><ul><li>world's largest current pandemic threat </li></ul><ul><li>billions of dollars are being spent researching H5N1 and preparing for a potential influenza pandemic </li></ul><ul><li>only a few antigenic shift mutations or antigenic drift mutations from being an avian influenza virus to being a human flu virus </li></ul>
  15. 34. NCBI Flu Database
  16. 35. Your Hypothesis <ul><li>State a hypothesis that can be tested by visualizing the genetic between different strains of virus. </li></ul><ul><li>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. </li></ul>