Orthomyxoviridae and Influenza Viruses
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Questions and Answers

What is the number of segments in the genome of the influenza virus A particle?

  • 9
  • 6
  • 8 (correct)
  • 7

    • What is the function of the hemagglutinin (HA) protein in the influenza virus?

  • To facilitate the entry of the virus into the host cell (correct)
  • To release the viral genome from the host cell
  • To encode the surface glycoproteins
  • To dissolve the viral envelope

    • What is the morphology of Orthomyxoviridae viruses?

  • Rigid and spherical in shape
  • Helical and spherical in shape
  • Flexuous and rod-shaped
  • Pleomorphic, with spherical, elongated, or filamentous shapes (correct)

    • What is the classification basis for influenza A virus subtypes?

    <p>The antigenic diversity of the surface glycoproteins</p> Signup and view all the answers

    What is unique about the replication of Orthomyxoviridae viruses?

    <p>They replicate in the nucleus</p> Signup and view all the answers

    How many subtypes of hemagglutinin (HA) are described in the influenza A virus?

    <p>18</p> Signup and view all the answers

    What is the genome of Orthomyxoviridae viruses composed of?

    <p>Single-stranded, segmented, negative-sense RNA</p> Signup and view all the answers

    What is the main reservoir of influenza A viruses?

    <p>Wild ducks</p> Signup and view all the answers

    What is the result of antigenic drift in the influenza virus?

    <p>The virus escapes immunity acquired after infection or vaccination</p> Signup and view all the answers

    What is the name of the gene that codes for hemagglutinin in influenza A viruses?

    <p>Segment 4</p> Signup and view all the answers

    What is the designation of the influenza A subtype that has a type 5 hemagglutinin (H) protein and a type 1 neuraminidase (N) protein?

    <p>H5N1</p> Signup and view all the answers

    What is the name of the gene that codes for nucleoprotein in influenza A viruses?

    <p>Segment 5</p> Signup and view all the answers

    What is the role of the neuraminidase (NA) protein in the influenza virus?

    <p>To cleave the sialic acid receptors on the host cell surface</p> Signup and view all the answers

    What is the source of the HA17 and NA10 subtypes of influenza A virus?

    <p>Bats</p> Signup and view all the answers

    How do influenza viruses undergo an antigenic change?

    <p>Through both antigenic drift and antigenic shift</p> Signup and view all the answers

    Which of the following genera of influenza viruses infects pigs, cattle, sheep, and goats?

    <p>Influenza virus D</p> Signup and view all the answers

    What is the process by which the genes encoding viral surface antigens undergo progressive mutation?

    <p>Antigenic drift</p> Signup and view all the answers

    What is the result of antigenic drift in the host?

    <p>The newly formed viruses can infect the host because of the absence of specific antibodies against the altered surface antigen</p> Signup and view all the answers

    What type of viruses can undergo antigenic shift?

    <p>Viruses with segmented genome</p> Signup and view all the answers

    What is the result of antigenic shift in influenza A viruses?

    <p>A new virus strain is released and can infect humans and also spread from person to person</p> Signup and view all the answers

    Why do the associated subtype of influenza virus change each year?

    <p>Due to development of immunological resistance to a previous year's strain</p> Signup and view all the answers

    What is the process by which two variants of a virus infect a single cell at the same time and produce a new virus strain?

    <p>Antigenic shift</p> Signup and view all the answers

    What is the consequence of a new virus strain emerging through antigenic shift?

    <p>The new virus strain can infect humans and also spread from person to person</p> Signup and view all the answers

    Which of the following is an example of a virus that can undergo antigenic shift?

    <p>Influenza A virus</p> Signup and view all the answers

    What is the most common season for influenza to occur in?

    <p>Winter</p> Signup and view all the answers

    Which of the following is a common symptom of influenza in adults?

    <p>Runny or stuffy nose</p> Signup and view all the answers

    What is the primary source of human H5N1 infection?

    <p>Close contact with diseased birds</p> Signup and view all the answers

    Which type of influenza virus can infect domestic poultry and other bird and animal species?

    <p>Type A influenza viruses</p> Signup and view all the answers

    What is the typical recovery period for most people who get the flu?

    <p>A few days to less than two weeks</p> Signup and view all the answers

    Which of the following avian influenza strains has been found in human infections following close bird exposure?

    <p>H7N9</p> Signup and view all the answers

    What is the typical host of swine influenza viruses?

    <p>Pigs</p> Signup and view all the answers

    What is the severity of illness that can be caused by influenza?

    <p>Mild to severe illness</p> Signup and view all the answers

    What is the characteristic of an influenza pandemic?

    <p>It spreads on a worldwide scale and infects a large proportion of the world population</p> Signup and view all the answers

    What is the subtype of the influenza virus that caused the 1918 flu pandemic?

    <p>H1N1</p> Signup and view all the answers

    What is the estimated number of people killed by the 1918 flu pandemic?

    <p>50 million to 100 million</p> Signup and view all the answers

    What is the name of the flu pandemic that occurred in 2009?

    <p>Swine flu pandemic</p> Signup and view all the answers

    What is the origin of the 2009 swine flu pandemic?

    <p>A combination of viruses from pigs, birds, and humans</p> Signup and view all the answers

    When did the World Health Organization (WHO) declare the H1N1 flu pandemic over?

    <p>August 2010</p> Signup and view all the answers

    What is the characteristic of the 1918 flu pandemic?

    <p>It was derived entirely from an avian source that adapted to humans</p> Signup and view all the answers

    What is the description of the 1918 flu pandemic?

    <p>The greatest medical holocaust in history</p> Signup and view all the answers

    Study Notes

    Orthomyxoviridae

    • Orthomyxoviridae is a family of viruses that have helical nucleocapsids and are enveloped with projections (spikes) evenly distributed over their surface.
    • They have single-stranded, segmented, negative-sense RNA genomes and replicate in the nucleus.
    • They infect a wide range of mammals (including humans) and birds.

    Influenza Viruses

    • Influenza viruses are the most important species belonging to the Orthomyxoviridae family.
    • There are four genera of Influenza virus: Influenza A, Influenza B, Influenza C, and Influenza D.
    • Influenza A virus infects humans, mammals (pigs, horses, whales, cats, bats), and birds, with wild ducks being the main reservoir of influenza A viruses.
    • Influenza B virus infects humans and seals, while Influenza C virus infects humans, pigs, and dogs.
    • Influenza D virus infects pigs, cattle, sheep, and goats, but no human infections have been recorded.

    Influenza A Virus Genome

    • Influenza A virus has a segmented RNA genome of negative sense, organized into 8 segments.
    • The segments are: Polymerase basic 2 gene (PB2), Polymerase basic 1 gene (PB1), Polymerase acidic gene (PA), Hemagglutinin gene (HA), Nucleoprotein gene (NP), Neuraminidase gene (NA), Matrix gene (M), and Non-structural gene (NS).

    Antigenic Change

    • Influenza viruses can undergo antigenic change in two ways: antigenic drift and antigenic shift.
    • Antigenic drift is a minor change that occurs through the accumulation of mutations over time, leading to a gradual change in the surface protein structure of the virus.
    • Antigenic shift (also called reassortment) is a more efficient process that occurs when two variants of the virus infect a single cell, resulting in the formation of new viruses with mixed genes from the two parent viruses.

    Human (Seasonal) Influenza

    • Each annual flu season is associated with a major influenza virus subtype, which changes each year due to the development of immunological resistance and mutational changes in previously circulating virus strains.
    • The most frequently circulating subtypes of influenza A viruses in the human population are H1N2, H3N2, and H1N1.
    • Influenza can cause mild to severe illness, and at times can lead to death.

    Avian Influenza

    • Avian influenza refers to the disease caused by infection with avian (bird) influenza (flu) Type A viruses.
    • These viruses occur naturally among wild aquatic birds worldwide and can infect domestic poultry and other bird and animal species.
    • Avian flu viruses do not normally infect humans, but sporadic human infections have occurred.

    Swine Influenza

    • Swine influenza (swine flu) is a respiratory disease of pigs caused by type A influenza virus.
    • Swine flu viruses do not usually infect humans, but rare human infections have occurred.

    Influenza Pandemic

    • An influenza pandemic is an epidemic of an influenza virus that spreads on a worldwide scale and infects a large proportion of the world population.
    • The most important influenza pandemics include the Spanish flu (1918 flu pandemic) and the Swine flu pandemic (2009).
    • The Spanish flu pandemic caused by an unusually severe and deadly Influenza A virus strain of subtype H1N1, killing an estimated 50 million to 100 million people worldwide.
    • The Swine flu pandemic (2009) was caused by a combination of viruses from pigs, birds, and humans, and was declared a pandemic by the World Health Organization (WHO) in 2009.

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    Learn about the characteristics of Orthomyxoviridae family of viruses and Influenza viruses, including their structure, genome, and hosts.

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