Virology Quiz on Virus Classification

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Questions and Answers

Which virus is classified under the hepevirus genus?

Hepatitis C virus

Rotavirus

Norwalk virus

Hepatitis E virus (correct)

What type of nucleic acid do reoviruses have?

Single-stranded DNA

Double-stranded linear RNA (correct)

Double-stranded circular DNA

Single-stranded RNA

Which major group of flaviviruses includes the dengue virus?

Retroviruses

Alphaviruses

Flaviviruses (correct)

Togaviruses

What characterizes orthomyxoviruses?

Helical nucleocapsid and single-stranded negative-polarity RNA Signup and view all the answers

What defines the presence of a viral envelope?

The presence of a lipid-containing membrane Signup and view all the answers

What term is used for a virus that lacks a lipid envelope?

Naked virus Signup and view all the answers

Which of the following viruses is part of the retrovirus group?

Human immunodeficiency virus (HIV) Signup and view all the answers

Which viruses are characterized by having an icockeheral capsid and positive-polarity RNA?

Togaviruses Signup and view all the answers

Which group of viruses contains double-stranded DNA?

dsDNA viruses Signup and view all the answers

Which of the following is a characteristic of enveloped viruses?

Flexible and coiled nucleocapsid Signup and view all the answers

What is the main human pathogen associated with reoviruses?

Rotavirus Signup and view all the answers

The hepadnavirus family, including hepatitis B virus, is classified as what type of virus?

Enveloped icosahedral virus Signup and view all the answers

Which viruses are human pathogens associated with respiratory infections?

Coronaviruses and respiratory syncytial virus Signup and view all the answers

What feature distinguishes paramyxoviruses from other enveloped viruses?

Helical nucleocapsid and nonsegmented negative-polarity RNA Signup and view all the answers

What type of RNA do rhabdoviruses possess?

Single-stranded, linear, nonsegmented, negative-polarity RNA Signup and view all the answers

Which of the following families of viruses is not enveloped?

Adenoviruses Signup and view all the answers

What is the diameter of papovaviruses?

55 nm Signup and view all the answers

What is the significance of the term 'filo' in filoviruses?

Indicates their shape resembling threads Signup and view all the answers

Which virus is recognized as the only significant human pathogen from the rhabdovirus family?

Rabies virus Signup and view all the answers

What type of genetic material do human papillomaviruses contain?

Double-stranded circular DNA Signup and view all the answers

How many cases of SARS were reported globally by the end of the outbreak?

8,300 cases Signup and view all the answers

What was the major impact of respiratory infection control procedures during the SARS outbreak?

Reduced spread within hospitals Signup and view all the answers

Which of the following diseases is caused by coronaviruses?

Common cold Signup and view all the answers

Which animal is believed to be the natural reservoir for SARS-CoV?

Horseshoe bat Signup and view all the answers

What platform utilizes mRNA technology in COVID-19 vaccines?

Pfizer-BioNTech COVID-19 vaccine Signup and view all the answers

Which of the following vaccines is categorized as a viral vector vaccine?

Oxford AstraZeneca vaccine Signup and view all the answers

What type of virus are parvoviruses classified as?

Naked nucleocapsid DNA virus Signup and view all the answers

Which families of viruses contain positive-polarity RNA?

Picornaviruses, caliciviruses, and retroviruses Signup and view all the answers

How are reoviruses classified based on their RNA structure?

Double-stranded RNA Signup and view all the answers

What type of vaccine is the Sinopharm vaccine?

Inactivated virus vaccine Signup and view all the answers

What kind of viruses are classified as enveloped RNA viruses?

Flaviviruses and coronaviruses Signup and view all the answers

Which vaccine mentioned is based on a protein-based platform?

Novavax vaccine Signup and view all the answers

What type of genome do adenoviruses possess?

Double-stranded linear DNA Signup and view all the answers

Which virus is a member of the hepadnavirus family?

Hepatitis B virus Signup and view all the answers

What is a characteristic feature of poxviruses?

Bricklike shape with complex capsid symmetry Signup and view all the answers

Which of the following is NOT a pathogen in the herpesvirus family?

Rhinovirus Signup and view all the answers

What is the diameter of the naked icosahedral adenoviruses?

75 nm Signup and view all the answers

Which description accurately fits caliciviruses?

Naked viruses with single-stranded linear RNA Signup and view all the answers

What is the function of the vaccinia virus?

Prevents smallpox Signup and view all the answers

Picornaviruses are known for which of the following characteristics?

Naked icosahedral viruses with positive-polarity RNA Signup and view all the answers

What is the primary mode of transmission for MERS to humans?

Close contact with camels Signup and view all the answers

What virus strain is responsible for COVID-19?

SARS-CoV-2 Signup and view all the answers

Which symptom is NOT commonly associated with COVID-19?

Skin rash Signup and view all the answers

What percentage of people infected with COVID-19 typically recover without special treatment?

80% Signup and view all the answers

What is the incubation period range for COVID-19?

1-14 days Signup and view all the answers

What is the low risk associated with MERS when considering person-to-person transmission?

Low risk in general population Signup and view all the answers

Who is more likely to develop serious illness from COVID-19?

Older people and those with underlying health issues Signup and view all the answers

When was COVID-19 officially declared a pandemic by WHO?

March 2020 Signup and view all the answers

Study Notes

Medical Important Viruses

Viruses are infectious agents, minimally constructed of a genome (RNA or DNA, not both) and a protein capsid to protect the genome.
Some viruses have additional features like a lipid-containing envelope.
A complete virus particle is called a virion.
Viruses can only reproduce within host cells.
A virion acts as a delivery system for the viral genome.
A virion's payload is its viral genome, which can include enzymes needed for viral replication.
Viral pathogenicity varies greatly within a closely related virus group and depends on structural and functional characteristics. This can lead to distinct clinical pathologies within the same family.

Virus Structure

Viruses are significantly smaller than the cells they infect (100-1000x smaller).
The smallest viruses are in the nanometer range (20nm in diameter), while some larger ones reach 300nm.
Smallpox virus, a large virus, overlaps the size of bacterial cells.
Viruses generally pass through filters designed to trap bacteria, making filterability useful for detecting viral etiology.

Virus Classification

Viruses are divided into related groups (families).
Subfamilies are further categorized based on factors such as the structure and type of viral nucleic acid, replication strategy, capsid symmetry (helical vs. icosahedral), and the presence of a lipid envelope.
Within a virus family, additional properties like host range, serological response, and amino acid sequences of viral proteins help further classify into genera and species.

Viral Genome

A virus genome can be either DNA or RNA, single-stranded, or double-stranded.
The most common viral genomes are ssRNA and dsDNA.
Single-stranded RNA genomes are further classified into positive and negative polarity.
Positive-polarity RNA (mRNA-sense) can be used as a template for proteins.
Negative-polarity RNA (asense) can't be directly used as a protein template but requires a complimentary RNA strand.

Viral Capsid Symmetry

The protein shell (capsid) that encloses the virus genome can have one of two geometric configurations.
Spherical (icosahedral) or rod-shaped (helical)
The capsid is built of multiple copies of one or a few different polypeptide types, which requires minimal genetic information.

Helical Symmetry

A helical symmetry structure is common in some virus families.
They consist of repeated polypeptide subunits (protomers); these self-assemble into a helical cylinder.
The protomer is hydrogen-bonded to neighboring protomers forming a nucleocapsid.

Icosahedral Symmetry

In icosahedral structures, the capsid is made of multiple copies of one or a few different polypeptide types.
These form capsomers, clustered into an icosahedron (a 20-sided geometrical figure with 12 vertices).

Viral Envelope

A virus's envelope is an important structural characterization feature determined by the presence or absence of a lipid-containing membrane that surrounds the nucleocapsid.
Enveloped viruses have a flexible and coiled nucleocapsid inside their envelope, appearing roughly spherical.
The envelope is derived from host cell membranes.
Virus-specific proteins replace cellular proteins, resulting in virus-specific antigenicity.

Viral Replication Cycle

Viral replication is a series of steps, starting from virus attachment to host cells to releasing viral progeny.
The steps include attachment, penetration, uncoating, gene expression and replication, assembly, and release.

Baltimore Classification

There are 7 groups of medically important viruses according to the Baltimore Classification system.
These are based on whether the genome is DNA or RNA and whether it is single-stranded or double-stranded, linear or circular.

DNA Viruses

There are three naked (non-enveloped), icosahedral families, which include parvoviruses, papovaviruses, and adenoviruses. A fourth enveloped, icosahedral group is the hepadnaviruses, family that includes hepatitis B virus.
The poxviruses are enveloped viruses with a complex internal symmetry, and they are the largest of the DNA viruses.

RNA Viruses

The three naked icosahedral virus families are presented first followed by the three enveloped icosahedral viruses.
All but three of the remaining families are enveloped helical viruses; the first five have single-stranded linear RNA, and the last three have single-stranded circular RNA.

Specific Virus Families (examples)

Picornaviruses: Smallest RNA viruses with single-stranded, linear, positive-polarity RNA within an icosahedral capsid. Common human pathogens are poliovirus, rhinovirus, and coxsackievirus.
Caliciviruses: Naked RNA viruses (38 nm) with single-stranded, linear positive-polarity RNA in an icosahedral capsid. Common culprits for foodborne outbreaks, like Norwalk virus.
Reoviruses: Naked viruses with double-stranded RNA, linear segmented genetic material in double icosahedral capsids. Rotavirus is a major cause of diarrhea in infants.
Flaviviruses: Enveloped, icosahedral, single-stranded, linear, positive-polarity RNA. Common viruses include hepatitis C, yellow fever, dengue, West Nile, and Japanese encephalitis viruses.
Togaviruses: Enveloped viruses with single-stranded, linear, positive-polarity RNA in an icosahedral capsid. Alphaviruses and rubiviruses are major human pathogens (e.g., eastern and western equine encephalitis, rubella virus).
Retroviruses: Enveloped viruses contain single-stranded linear, positive, nonsegmented RNA. This class includes human immunodeficiency virus (HIV) and leukemia viruses.
Orthomyxoviruses: Enveloped, helical, single-stranded RNA genome with nonsegmented, negative-polarity RNA. Influenza viruses.
Paramyxoviruses: Enveloped viruses with a helical nucleocapsid and nonsegmented negative RNA. Includes measles, mumps, and respiratory syncytial viruses.
Rhabdoviruses: Bullet-shaped, enveloped viruses with a helical capsid containing nonsegmented, negative-polarity RNA. Rabies is an important human pathogen.
Filoviruses: Enveloped viruses, highly pleomorphic, filamentous morphology. Contains single-stranded, negative, nonsegmented RNA. Ebola and Marburg are notable human pathogens.
Coronaviruses: Enveloped, helical, nonsegmented, positive-polarity RNA. Common cold, SARS, MERS, COVID-19 are significant human diseases caused by coronaviruses.

Viral Diseases (examples)

SARS, MERS, COVID-19 are noteworthy disease caused by coronaviruses.
Measles, mumps, parainfluenza, and respiratory syncytial viruses are major human pathogens caused by paramyxoviruses.
Rabies is a deadly human illness caused by the rhabdovirus.

COVID-19-Specific Information

COVID-19, caused by SARS-CoV-2, is a severe acute respiratory syndrome coronavirus (SARS-CoV-2)
SARS-CoV-2 was identified in Wuhan, China, and characterized as a pandemic.
Incubation period: 1-14 days.

Prevention and Diagnosis

Handwashing, avoiding sick people, wearing masks, and avoiding crowded places are helpful preventative measures.
Molecular tests like PCR and antibody tests are used to detect active infections and prior exposure to the virus.

References

Various publications (see slide 57)
Websites (see slides 45,49, and 53)

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Description

Test your knowledge on various virus classifications and characteristics with this engaging quiz. Questions cover a range of virus types, including hepeviruses, reoviruses, flaviviruses, and retroviruses. Perfect for students and enthusiasts of virology seeking to deepen their understanding of viral biology.