, Respiratory Syncytial Virus '

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• ????, Respiratory Syncytial Virus ??? ???? ?????
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Influenza Activity During 2001-2002 Season

• Based on reports from national influenza centers
  to WHO

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Influenza Activity During 2001-2002 Season

• Outbreaks of influenza were reported in
  Australia, Canada and the Philippines during the
  first week of October.  Activity in the USA was
  reported to be at local outbreak level on the
  second week of November and viruses isolated were
  influenza A and B. .

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Influenza Activity During 2001-2002 Season

• In other countries that reported, the rate of
  acute respiratory consultations remained below
  baseline levels.
• All influenza viruses studied are similar to the
  current vaccine strains.

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????? ?????Influenza viruses (Influenzavirus)

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• ???? ???? ?????

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Taxonomy

• Family Orthomyxoviridae

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????? ?????Influenza viruses (Influenzavirus)

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• ?????? ???????
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• ????? (Spikes)
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Family Orthomyxoviridae

• 1.Genus Influenzavirus A
• Type species influenza A virus
• 2.Genus Influenzavirus B
• Type species influenza B virus
• 3.Genus Influenzavirus C
• Type species influenza C virus
• 4.Genus Thogotovirus
• Type species Thogoto virus

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????? ?????Influenzavirus A

• Virions enveloped
• About 500 spikes
• Nucleocapsid enclosed within lipoprotein membrane
• Virions contain 8 segments of linear
  negative-sense single stranded RNA
• Total genome length is 13588 nt
• The largest segment 2341 nt

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????? ?????Influenzavirus B

• Virions enveloped
• About 500 spikes
• Nucleocapsid enclosed within lipoprotein membrane
• Virions contain 8 segments of linear
  negative-sense single stranded RNA
• Total genome length is 13588 nt
• The largest segment 2341 nt

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????? ?????Influenzavirus C

• Virions enveloped
• Many spikes
• Nucleocapsid enclosed within lipoprotein membrane
• Virions contain 7 segments of linear
  negative-sense single stranded RNA
• Total genome length is 12900 nt
• The largest segment 2300-2500 nt

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OrthomyxovirusesInfluenza A Viruses

• Infect a wide variety of mammals, including man,
  horses, pigs, ferrets and birds.
• Pigs and birds are believed to be particularly
  important reservoirs, generating pools of
  genetically/antigenically diverse viruses which
  get transferred back to the human population via
  reassortment (close contact between pigs and man
  in the far east Ducks - migration!).
• The main human pathogen, associated with
  epidemics and pandemics.

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OrthomyxovirusesInfluenza B Viruses.

• Infect much man and birds.
• Cause human disease but generally not a severe as
  A types.
• Believed to be epidemiologically important -
  reassortment with type A leads to epidemics.

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OrthomyxovirusesInfluenza C Viruses.

• Influenza C viruses infect man alone, but do not
  cause disease (?). they are genetically and
  morphologically distinct from A and B types -
  little studied.

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Influenza Viruses. Morphology

• Influenza virus particles are highly pleomorphic,
  mostly spherical/ovoid, many forms occur.
• The outer surface of the particle consists of a
  lipid envelope from which project prominent
  glycoprotein spikes.
• The inner side of the envelope is lined by the
  matrix protein.
• The genome segments are packaged into the core.

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Influenza Viruses. Replication
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Influenza Viruses. Replication

• ??????? ????? ????? ??? ????? ????? ?????.
• After binding, the particle is engulfed by
  endocytosis via coated pits (?????) into
  endocytotic vesicles and finally endosomes.
• Specific nuclear targeting sequences result in
  translocation of the nucleocapsid (?????? ??????)
  into the nucleus.

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Influenza Viruses. Replication
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Influenza Viruses. Replication

• Virus particles are gradually released from the
  surface of the cell over a period of several
  hours. The cell does not lyse, but eventually
  dies (due to disturbance of normal cellular
  macromolecular synthesis?).

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Influenza. Pathogenesis

• Spread is by aerosols.
• Primary infection involves the ciliated
  epithelial cells.
• Necrosis of these cells results in the usual
  symptoms of the acute respiratory infection
  (fever, chills, muscular aching, headache,
  prostration, anorexia).

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Influenza. Pathogenesis

• Normally self-limited infection usually lasts 3-7
  days (???? ?????).
• Death from primary influenza infection is very
  rare and appears to be determined by host factors
  rather than 'virulence' of virus.
• Damage to respiratory epithelium predisposes to
  secondary bacterial infections which accounts for
  most deaths.