Medical Important Viruses
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Questions and Answers

What is a key structural feature for classifying a virus as enveloped or naked?

  • Presence of double-stranded RNA
  • Presence of a lipid-containing membrane (correct)
  • Surface proteins
  • Nucleocapsid shape

    • Which virus family is classified as a naked icosahedral virus?

  • Papovaviruses (correct)
  • Hepadnaviruses
  • Poxviruses
  • Herpesviruses

    • What does the presence of virus-specific proteins in an envelope confer?

  • Virus-specific antigenicity (correct)
  • Increased replication speed
  • Stability to the virus
  • Resistance to host immune response

    • Which of the following viruses is classified as a (-)ssRNA virus?

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

    Which step in the viral replication cycle follows gene expression?

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

    What characteristic of enveloped viruses usually affects their appearance?

    <p>They appear roughly spherical.</p> Signup and view all the answers

    Which of the following viruses is associated with progressive multifocal leukoencephalopathy?

    <p>JC virus</p> Signup and view all the answers

    What is the diameter of the papovavirus family?

    <p>55 nm</p> Signup and view all the answers

    What are the two main components that make up a virus?

    <p>Genome and capsid</p> Signup and view all the answers

    What term is used to describe a complete virus particle?

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

    Which of the following characteristics is NOT used to classify virus families?

    <p>Size of the virion</p> Signup and view all the answers

    How does the pathogenicity of a virus vary among closely related species?

    <p>It can differ significantly due to structural and functional characteristics.</p> Signup and view all the answers

    What is the approximate diameter of the smallest human viruses?

    <p>20 nm</p> Signup and view all the answers

    What structural feature enhances the ability of some viruses to evade filtration designed to trap bacteria?

    <p>Virion size</p> Signup and view all the answers

    Which of the following statements is true regarding viral envelopes?

    <p>The presence or absence of an envelope distinguishes different virus groups.</p> Signup and view all the answers

    What is the term used to describe the capacity of a virus to infect and cause disease in host cells?

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

    What forms the basis for the division of viruses into genera and species?

    <p>Differences in specific properties like host range and serologic reactions</p> Signup and view all the answers

    Which type of RNA virus can be used directly as a template for protein synthesis?

    <p>Positive-strand RNA viruses</p> Signup and view all the answers

    What is the primary structural feature of helical capsids?

    <p>Form a helical cylinder from a single polypeptide species</p> Signup and view all the answers

    How are capsomers in icosahedral capsids organized?

    <p>Grouped into structural subassemblies</p> Signup and view all the answers

    What is a primary characteristic of viruses with double-stranded RNA genomes?

    <p>They consist of two complementary RNA strands.</p> Signup and view all the answers

    What do the helical and icosahedral configurations of capsids primarily refer to?

    <p>The geometric structure of the protein coat surrounding the genome</p> Signup and view all the answers

    What type of viral genome is known to be positive polarity?

    <p>RNA used as a template for protein synthesis</p> Signup and view all the answers

    Which statement accurately describes the nucleocapsid in viral structure?

    <p>It consists of protomers and the associated nucleic acid.</p> Signup and view all the answers

    What type of DNA do adenoviruses possess?

    <p>Double-stranded linear DNA</p> Signup and view all the answers

    Which virus family is known for causing latent infections?

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

    What is the size and structure of hepadnaviruses?

    <p>Double-shelled with an envelope and double-stranded circular DNA</p> Signup and view all the answers

    Which of the following viruses is used in the smallpox vaccine?

    <p>Vaccinia virus</p> Signup and view all the answers

    What type of genetic material do picornaviruses contain?

    <p>Single-stranded linear nonsegmented positive-polarity RNA</p> Signup and view all the answers

    Which of the following is NOT a pathogen associated with herpesviruses?

    <p>Hepatitis B virus</p> Signup and view all the answers

    Caliciviruses are characterized by which of the following features?

    <p>Naked virus with single-stranded linear positive-polarity RNA</p> Signup and view all the answers

    Which family of viruses is associated with causing respiratory tract diseases?

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

    What is the primary human pathogen associated with reoviruses?

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

    Which group of viruses does hepatitis C virus belong to?

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

    What characteristic defines retroviruses?

    <p>Enveloped with diploid RNA strands</p> Signup and view all the answers

    Which pathogen is primarily associated with the alphavirus group?

    <p>Eastern and Western encephalitis viruses</p> Signup and view all the answers

    What feature distinguishes orthomyxoviruses from other virus families?

    <p>Negative-polarity RNA with eight segments</p> Signup and view all the answers

    Which of the following viruses is NOT classified under Togaviruses?

    <p>Dengue virus</p> Signup and view all the answers

    What describes the structure of paramyxoviruses?

    <p>Enveloped with helical nucleocapsid</p> Signup and view all the answers

    Which virus is known to be associated with mucins due to its affinity?

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

    Which category of coronavirus vaccines are based on mRNA technology?

    <p>Pfizer-BioNTech COVID-19 vaccine</p> Signup and view all the answers

    What type of virus is the Johnson & Johnson COVID-19 vaccine based on?

    <p>Viral vector</p> Signup and view all the answers

    Which viral family includes RNA viruses that do not have an envelope?

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

    Which of the following vaccines is based on inactivated virus technology?

    <p>Sinovac vaccine</p> Signup and view all the answers

    What is the genetic material type of parvoviruses?

    <p>Single-stranded DNA</p> Signup and view all the answers

    Which of the following statements is true regarding RNA viruses?

    <p>Coronaviruses have positive-polarity RNA.</p> Signup and view all the answers

    Which vaccine is categorized as a protein-based vaccine?

    <p>Novavax vaccine</p> Signup and view all the answers

    What defines the classification of viruses primarily?

    <p>Nature of the genome and envelope status</p> Signup and view all the answers

    Study Notes

    Medical Important Viruses

    • Viruses are infectious agents, minimally constructed of a genome (RNA or DNA, but not both) and a protein-containing structure (capsid).
    • Some viruses have additional features like an envelope (lipid bilayer).
    • A complete virus particle is called a virion.
    • Viruses replicate inside host cells.
    • Viral pathogenicity depends on structural and functional characteristics.
    • Different viruses within a family may have different clinical pathologies.
    • Viruses are significantly smaller than cells (100-1000x smaller).
    • Viruses pass through filters designed to trap bacteria.
    • Viruses are classified into families, genera, and species based on characteristics like viral nucleic acid type, replication strategy, capsid symmetry, and presence of an envelope.
    • Viruses have a protein shell (capsid) that encloses the genome, either helical or icosahedral in structure.
    • The capsid is constructed of multiple copies of a single or several polypeptides.
    • The nucleocapsid is the complex of protomers and nucleic acid.
    • Some viruses have an envelope, derived from host cell membranes, which is important for classifying viral families.
    • The envelope is composed of a lipid bilayer with viral proteins.
    • Viruses have various single- or double-stranded genomes, often RNA.
    • Positively-polarity RNA can be directly used as a protein synthesis template.
    • Negatively-polarity RNA requires complementary mRNA for protein synthesis.
    • Viral replication involves attachment, penetration, uncoating, gene expression, replication, assembly, and progeny release.

    Viral Classification

    • Viruses are classified based on their genome type (DNA or RNA), strandedness, and symmetry.
    • Baltimore classification system categorizes viruses into seven groups based on their genome and mechanism of mRNA production.
    • Example groups include dsDNA, ssDNA, dsRNA, (+)ssRNA, (-)ssRNA, (+)ssRNA-RT, and dsDNA-RT.

    Summary of Important Virus Families

    • DNA Viruses: Naked icosahedral viruses (parvoviruses, papovaviruses, adenoviruses); enveloped icosahedral viruses (herpesviruses, hepadnaviruses); poxviruses (complex internal symmetry).
    • RNA Viruses: Naked icosahedral viruses (picornaviruses, caliciviruses, reoviruses); enveloped helical viruses (influenza, mumps, measles, parainfluenza, respiratory syncytial viruses), enveloped icosahedral viruses (togoviruses, flaviviruses); retroviruses, bullet-shaped viruses (filoviruses) with helical nucleocapsid, single stranded linear non-segmented RNA, nonsegmented RNA

    Specific Virus Examples (with examples of diseases they cause)

    • Adenoviruses: Mild respiratory infections, some cancers.
    • Papovaviruses: Progressive multifocal leukoencephalopathy, some cancers.
    • Herpesviruses: Herpes simplex, varicella-zoster, cytomegalovirus, Epstein-Barr virus (various infections).
    • Hepadnaviruses: Hepatitis B
    • Poxviruses: Smallpox, monkeypox (various skin lesions)
    • Picornaviruses: Polio, common cold, hepatitis A (various diseases)
    • Caliciviruses: Norovirus (gastroenteritis).
    • Reoviruses: Rotavirus (diarrhea).
    • Togaviruses: Rubella virus (German measles), several encephalitis viruses.
    • Flaviviruses: Yellow fever, dengue, West Nile encephalitis (various diseases).
    • Retroviruses: HIV (AIDS) human T cell leukemia viruses.
    • Orthomyxoviruses: Influenza viruses
    • Paramyxoviruses: Measles, mumps, parainfluenza, respiratory syncytial viruses (respiratory infections).
    • Rhabdoviruses: Rabies
    • Filoviruses: Ebola virus, Marburg virus (severe hemorrhagic fever).
    • Coronaviruses: Common colds, SARS, MERS, COVID-19 (severe respiratory infections)

    Additional notes

    • Coronavirus disease 2019 (COVID-19) is caused by the SARS-CoV-2 SARS Virus.
    • Various molecular diagnostic tests (nucleic acid detection, serology) are used to identify and diagnose active or recent infections with some viruses.
    • Different types of COVID-19 vaccines are now widely available including mRNA based vaccines (Pfizer, Moderna), inactivated virus vaccines (Sinovac, Sinopharm), and viral vector vaccines (Oxford/AstraZeneca, Sputnik).
    • Unvaccinated individuals are 17 times more likely to be hospitalized with Covid-19.
    • COVID-19 vaccines are effective against infection and severe illness from related viruses.

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    Description

    This quiz explores the fundamental concepts of important viruses, including their structure, replication, and classification. Understand the key differences in viral families, their pathogenicity, and the characteristics that define various viruses. Perfect for students studying virology or infectious diseases.

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