Viruses

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Viruses
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The word Virus comes from the Latin word meaning
poison.
Tobacco mosaic virus stunts the growth of tobacco
plants and gives their leaves a mottled, mosaic
coloration.
Studied as early as 1883 by Adolf Mayer, but
basically could not be grown in a lab, could not
be filtered or seen with a microscope.
Was not isolated and identified until 1935 by an
American scientist Wendell Stanley.
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A virus consists of either DNA or RNA enclosed in
a protein shell or coat called a capsid.
Some viruses are also covered by a membranous
envelope that is derived from the membrane of the
host cell. ( Influenza has this, it is called
enveloped)
Sooooooo small, that they are seen only with an
electron microscope
A virus is an intracellular parasite that can
reproduce only by taking over a host cells
equipment.
They do not feed, grow, reproduce, take in or
release energy outside of the host cell.
They have no cell parts no cytoplasm, no
organelles, no cell membrane.
They may attack plants, animals, bacteria,
protists.
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Viral Diseases

• Cold
• Flu
• Polio
• Measles
• Herpes virus Chicken pox (herpes zoster),
  shingles, cold sores, infectious mononucleosis,
  genital herpes
• Mumps
• Rabies (attacks CNS of warm blooded animals
  foxes, skunks, bats, raccoons)
• HIV
• SARS (coronavirusupper respiratory infections)
• Hepatitis (liver damage)
• Ebola, Marburg ( hemorrhagic)
• Papillomavirus (warts)

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Herpes zoster
Ebola
Bird Flu
Cold virus
polio
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Bacteriophage
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Bacteriophage or Phage Virus attack bacterial
cells
Contractile sheath
Tail
Tail fibers
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Lytic Cycle
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Lytic and Lysogenic cycle
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Naming flu viruses

• Influenza viruses are defined by two protein
  components, known as antigens on the surface of
  the virus
• Haemagglutinin (H) and Neuraminidase (N)
• Influenza viruses that cause human disease are
  divided into two groups A and B
• Influenza A has two subtypes that are important
  for humans A(H3N2) and A(H1N1).
• The numbers refer to slight variations
• Avian Flu (H5N1)
• Large-scale outbreaks are called epidemics. If
  they spread worldwide, they're called pandemics.

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Flu Vaccines

• Flu vaccines must be reformulated from scratch
  every year to keep pace with the mutations of
  influenza viruses.
• The process is a long one, lasting close to a
  year
• In Canada the flu season runs from November to
  April.
• Beginning in February the WHO studies the new
  strain mutations for next winters vaccination.
• 83 countries provide information to the WHO and a
  vaccine is created that targets the three most
  virulent strains in circulation

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• The vaccines are developed using fertilized chick
  eggs
• The shell of a 10-day old is cracked and the flu
  virus injected into the fluid surrounding the
  embryo
• The egg is resealed allowing the embryo to become
  infected
• The virus is harvest two days later
• A single egg is required to make one dose of a
  vaccine strain, requiring the use of 10s x
  millions of eggs every year

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• Flu vaccines are available as a shot or nasal
  mist.
• The shot contains killed flu viruses that won't
  cause you to get the flu, but will make your body
  create antibodies that fight off infection if you
  encounter the live flu virus.
• The nasal mist contains weakened live flu
  viruses. Because it contains live viruses, the
  mist is not for people with weakened immune
  systems or certain health conditions. It is only
  for healthy, non-pregnant, people between the
  ages of 2 and 49 years.