Influenza H5N1

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Influenza H5N1

• By Steven Yi

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Contents

1. Overview
2. History
3. Attachment
4. Entry
5. Replication
6. Lytic Cycle
7. Diagnosis
8. Treatment

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Overview

• Influenza, or, more commonly, the flu, is an
  infectious disease caused by single-stranded RNA
  viruses from the family Orthomyxoviridae. H5N1 is
  a particularly pathogenic strain adapted to avian
  populations. Over 60 of confirmed victims of
  avian flu have died, but there only seems to be
  limited human-to-human communication of the
  disease. If this strain were to become
  communicable between humans, a severe pandemic
  would be likely.

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History

• In 1997, H5N1 first materialized as an extremely
  lethal strain of avian flu a disease that had
  hitherto only produced minor sickness. The
  disease that materialized was capable of rapidly
  killing poultry and required the culling of
  millions of animals to contain the spread of the
  disease. Hong Kong culled its entire domestic
  population.
• Since then, hundreds of outbreaks were reported
  in Asia. One of the things that make this strain
  of avian flu so dangerous is its capacity to
  mutate. Huge amounts of money have been spent by
  the US and other countries in anticipation of
  H5N1 mutating into a form capable of spreading
  from human to human. Without adequate
  preparation, such an outbreak could potentially
  take out a significant portion of the human
  population.

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Attachment and Entry

• Influenza viruses bind to sialic acids on the
  surfaces of epithelial cells, such as those found
  in the nose, throat, and lungs, and red blood
  cells via antibodies called hemaglutinin.
• The cell then engulfs the virus through
  endocytosis. The virus then injects its vRNA, RNA
  polymerase, and accessory proteins into the host
  cells cytoplasm. These materials are then
  transported to the nucleus of the cell.

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Replication Lytic Cycle

• RNA polymerase transcribes negative- sense vRNA
  into positive-sense (translatable into proteins)
  vRNA. The vRNA then either remains in the nucleus
  or is transported into the cytoplasm, where it is
  translated into viral proteins. These are then
  either secreted by the Golgi body to the cell
  surface, or transported back into the nucleus to
  be combined with negative-sense vRNA and
  assembled into new viruses.
• Meanwhile, other proteins assist in degrading
  host mRNA or inhibiting the translation of host
  mRNA. Nucleotides from the former for vRNA
  synthesis.
• New viruses do not exit the cell by lysing the
  membrane instead, they bud off the host cell,
  taking with them a portion of the plasma
  membrane. The host cell is now dead.

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Symptoms

• Fever
• Cough
• Aches
• Sneezing
• General discomfort
• Problems breathing
• Pneumonia
• Sore throat
• Conjunctivitis

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Treatment

• There are currently no effective treatments for
  H5N1. Mainly, drugs such as Tamiflu are used that
  act as asneuraminidase inhibitors that prevent
  the virus from adhering to the cell membrane.
• The constant and rapid evolution of H5N1 renders
  vaccines and largely ineffective. Only good
  hygiene and safe, cautious practices can hope to
  limit the spread of an H5N1 outbreak, should one
  occur in the near future.