Virology Quiz on Arboviruses

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Questions and Answers

What type of viruses are primarily transmitted to humans by the bite of a mosquito or tick?

Bovine viral diarrhea viruses

Alphaviruses

Hepatitis C viruses

Flaviviruses (correct)

Which clinical syndrome is associated with the yellow fever virus?

Aseptic meningitis

St. Louis encephalitis

Hemorrhagic fever (correct)

Dengue shock syndrome

What is the primary structure formed by the capsid protein and the viral RNA in flaviviruses?

Lipid bilayer

Icosahedral nucleocapsid (correct)

Viral membrane

Viral envelope

Which of the following is a characteristic of dengue hemorrhagic fever?

Significant mortality if untreated Signup and view all the answers

How are hepatitis C viruses classified?

Based on their nucleotide sequences Signup and view all the answers

What is the most common serious complication of varicella?

Varicella pneumonia Signup and view all the answers

Which of the following is a recommended action for preventing Reye syndrome in children following VZV infection?

Using non-salicylate medications for fever Signup and view all the answers

What is the incubation period for human cytomegalovirus (HCMV)?

4-8 weeks Signup and view all the answers

In immunodeficient patients, which of the following conditions can HCMV cause?

Pneumonia Signup and view all the answers

What mechanism primarily establishes latency in HCMV infections?

Infection of monocytes and macrophages Signup and view all the answers

What is the relationship between HCMV and asymptomatic infections in children?

Children shed the virus considerably for months Signup and view all the answers

Which symptom is NOT associated with primary HCMV infection in adults?

Rash Signup and view all the answers

How is HCMV primarily transmitted among adults?

Via sexual contact and bodily fluids Signup and view all the answers

What type of genome do adenoviruses possess?

Double-stranded linear DNA Signup and view all the answers

Which of the following diseases is commonly associated with adenoviruses?

Acute febrile pharyngitis Signup and view all the answers

Adenoviruses are primarily transmitted through which route?

Respiratory route Signup and view all the answers

What type of conjunctivitis is associated with adenovirus infections and particularly prevalent in children?

Pharyngoconjunctival fever Signup and view all the answers

Which of the following is a common method of transmission for epidemic keratoconjunctivitis?

Shared towels Signup and view all the answers

What types of viruses are included in the Paramyxovirinae subfamily?

Paramyxovirus, Rubulavirus, and Morbillivirus Signup and view all the answers

Which serotypes of adenoviruses are specifically associated with infantile gastroenteritis?

Serotype 40 and 41 Signup and view all the answers

What is horizontal transmission in the context of plant viruses?

Introduction of a virus from outside using insect vectors. Signup and view all the answers

What condition may develop from respiratory syndromes caused by adenoviruses, particularly in infants?

True viral pneumonia Signup and view all the answers

Which enzyme is not present in the Measles virus?

Neuraminidase Signup and view all the answers

Which type of transmission occurs when a virus is passed from a plant to its offspring?

Vertical transmission Signup and view all the answers

Which statement is true regarding the gastrointestinal diseases caused by adenoviruses?

They are generally asymptomatic. Signup and view all the answers

Which of the following describes the structure of paramyxoviruses?

Spherical, enveloped with a non-segmented negative-strand RNA genome Signup and view all the answers

What symptoms are primarily caused by human parainfluenza viruses (hPIV)?

Croup, pneumonia, and bronchiolitis Signup and view all the answers

What distinguishes viroids from viruses?

Viroids contain only ssRNA and do not code for proteins. Signup and view all the answers

What is the nature of the genome in most plant viruses?

Single-stranded RNA Signup and view all the answers

Which component of the paramyxovirus is responsible for facilitating virus entry into the host cell?

F protein Signup and view all the answers

What is the main clinical impact of the mumps virus?

Primarily causes acute parotitis and orchitis Signup and view all the answers

Which of the following best describes prions?

Self-replicating proteins causing neurodegenerative disorders. Signup and view all the answers

What kind of infections do papovaviruses induce?

Both lytic infections and tumors. Signup and view all the answers

Which characteristic distinguishes the Paramyxovirus from other viruses?

Presence of both hemagglutinating and neuraminidase activities Signup and view all the answers

What enables viral particle movement through plant cells during an infection?

Plasmodesmata Signup and view all the answers

Which is true regarding the viral replication and assembly of paramyxoviruses?

Their mRNA transcription resembles that of rhabdoviruses Signup and view all the answers

Which subfamily of non-enveloped DNA viruses is known for causing hyperplastic epithelial lesions?

Papillomavirinae Signup and view all the answers

What is the role of phage-encoded enzymes during viral replication?

To degrade host nucleic acids and provide nucleotide building blocks Signup and view all the answers

What occurs during the eclipse period of viral infection?

The host cell contains components of phage but no complete viral particles Signup and view all the answers

What defines the latent period in the viral life cycle?

Time between phage attachment and the release of new phages Signup and view all the answers

What happens when a temperate phage enters the lysogenic cycle?

Phage DNA becomes part of the host’s genome as a prophage Signup and view all the answers

Which factor typically triggers the transition from lysogenic to lytic cycle in temperate phages?

Environmental stressors such as UV light Signup and view all the answers

What is the primary function of repressor proteins in the lysogenic phase?

To inhibit transcription of most phage genes Signup and view all the answers

What characterizes virulent phages?

They cause the immediate lysis of their host cells Signup and view all the answers

Which example represents a temperate phage?

Bacteriophage Lambda (λ) Signup and view all the answers

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Study Notes

Virology: Chapter 1: The Virus

A virus is a small infectious agent that replicates only inside living cells of other organisms
Viruses can infect all types of life forms, from animals and plants to microorganisms, including bacteria and archaea
Viruses are grouped according to their genetic material: DNA or RNA
Viruses are too small to be seen with a light microscope
Viruses are obligate intracellular parasites, requiring living host cells to multiply
Viruses contain a single type of nucleic acid: either DNA or RNA (not both)
The virion* consists of a nucleic acid core (genome) surrounded by a protein coat (capsid)
The nucleocapsid is the capsid together with the enclosed nucleic acid
Some viruses are surrounded by envelopes of lipid, proteins, and carbohydrates
Viruses replicate by assembling individual components, not by division
Viruses do not have their own metabolic machinery; they use the host cell's machinery to produce their components
Viruses that infect bacteria are called bacteriophages or phages

Introduction

Viruses are too small to be seen with a light microscope.
Unlike other infectious agents, viruses require living host cells to multiply
Viruses are filterable agents, passing through filters that retain bacteria
A single virus particle (virion) contains a single type of nucleic acid (either DNA or RNA) within a protein coat (capsid)
The capsid, along with the nucleic acid, is called the nucleocapsid
Some viruses have an envelope surrounding the nucleocapsid
Viruses replicate by assembling individual components, not through cell division
Viruses lack their own metabolic machinery, requiring the host cell's systems for replication
Bacteriophages are viruses that infect bacteria

Bacteria vs viruses

Feature	Bacteria	Viruses
Living Attributes	Living	Not living (organic structure interacting with living organisms)
Cell Number	Unicellular (one cell)	No cells
Structures	DNA, RNA, cell wall, cell membrane	DNA or RNA enclosed inside a protein coat
Ribosomes	Present	Absent
Enzymes	Yes	Absent (or few - using host cell components)
Nucleus	Present	Absent
Disease Causation	Yes	Yes
Treatment	Antibiotics	Vaccines and antiviral meds (cannot stop reproduction completely)
Reproduction	Fission (asexual)	Host cell takes over to produce copies of the viral genome
Size	Larger (1,000nm)	Smaller (20-400nm)

Structure of a virus

The virion consists of a nucleic-acid core (genome) and a protein coat (capsid)
The capsid + enclosed nucleic acid = nucleocapsid
Some viruses have an envelope surrounding the nucleocapsid
Enveloped Viruses: Have an outer lipid membrane derived from the host cell
Non-enveloped Viruses: Lack an outer lipid membrane

Viral Structure

Viral structure is characterized by symmetry(icosahedral symmetry, helical symmetry, or complex symmetry), which the arrangement of capsomeres (protein subunits) determines.
The nucleocapsid=capsid + genome
The presence of an envelope, derived from the host cell's membrane, is a characteristic feature of some viruses
Attachment proteins project from the capsid and bind to host receptors

Viral Classification

Viruses are classified by their morphological type (helical, polyhedral, enveloped, complex)
Helical viruses have rod-like shapes, either rigid or flexible
Polyhedral viruses are multi-sided, often icosahedral (with 20 triangular faces)
Enveloped viruses have an outer lipid envelope
Complex viruses have complicated structures, such as bacteriophages

1 - The Capsid

The capsid is a protein coat surrounding the nucleic acid core
It is made up of repeating protein subunits called capsomeres
Capsid functions:
- Impenetrable protective shell for the nucleic acid core
- Facilitates viral entry into host cells by adsorption to cell surfaces
- Protects the nucleic acid from nucleases in biological fluids

Basic Virus Structure

DNA or RNA + Capsid protein → Nucleocapsid = Naked capsid virus
Nucleocapsid + Lipid membrane, glycoproteins → Enveloped virus

2 - The Envelope

Enveloped viruses have an outer envelope derived from the host cell membrane, often with viral glycoproteins
Viruses lacking an envelope are termed "naked" or "non-enveloped" viruses
The lipid bilayer component of the envelope is usually of host cell origin

3 - Viral Symmetry

Icosahedral symmetry: Spherical or polyhedral shape. Typical for many viruses.
Helical symmetry: Rod-like or filamentous structure.
Complex symmetry: Irregular shape, often found in bacteriophages

Viral Multiplication

Lytic cycle: Virus replicates and lyses the host cell
Lysogenic cycle : The viral DNA is integrated into the host DNA, and the virus replicates along with the host cell.

4 - Viral Nucleic Acid, Proteins, and Lipids

Viruses contain nucleic acids (DNA or RNA); the type and number of nucleic acids vary among viruses
Viral proteins are involved in forming the capsid
Viral proteins have antigenic specificity that varies between viruses
Enveloped viruses contain lipids derived from the host cell membrane

1- The Capsid

The nucleic acid in a virus is surrounded by a protein coat called the capsid,
The capsid is composed of protein subunits (polypeptides) called capsomeres,
The arrangement of capsomeres is characteristic of a particular type of virus
The capsid protects the nucleic acid and helps in the attachment of the virus to the host cell.

Stages in a viral replication cycle

Each viral replication cycle has distinct phases :
- Attachment : Virus binds to specific receptors on host cell surface
- Penetration : Virus enters cell by endocytosis or fusion.
- Uncoating: Release of viral nucleic acid from its protein coat
- Biosynthesis: Synthesis of viral components (DNA/RNA and proteins)
- Assembly : Assembly of newly made viral components into complete virions
- Release : Release of nascent virions (lysis or budding)

Lytic Cycle

Phage-encoded lysozyme weakens the cell wall, and leads to lysis of the cell
Phage-encoded lysozyme → the host cell releases numerous viral progeny (infectious virions
The phage genes cause host cell's protein and nucleic acid synthesis to shut off

Adsorption (attachment)

HIV attaches via specific tail fiber proteins
The virus particle gains entry to the cell through interaction with complementary receptors on its surface.

Replication (DNA Viruses)

The DNA of animal cells, unlike that of bacteria, replicates in the nucleus
Messenger RNA passes to ribosomes in the cytoplasm for translation
The translation products are returned to the nucleus for assembly into new virus particles
Release of naked (non-enveloped) viruses occurs by host cell lysis, while enveloped viruses bud out from the host cell membrane.

DNA Viruses (Deoxyriboviruses)

Family name, genus name, example virus, size, molecular mass, DNA structure.

RNA Viruses (Riboviruses)

Family name, genus name, example virus, size, RNA structure.

Viral Symmetry

The arrangement of the viral capsid around the nucleic acid core determines the symmetry of the capsid.
Icosahedral symmetry (spherical viruses). Many viruses are icosahedral
Helical symmetry (rod-like or filamentous viruses).

Viral Nucleic Acid, Proteins, and Lipids

All viruses contain either DNA or RNA, NOT both.
The genome can be single-stranded or double-stranded, linear or circular.
Viral proteins constitute the capsid, protecting the nucleic acid, and possessing antigenic specificity that varies among viruses.
Enveloped viruses have an outer lipid membrane derived from the host cell membrane.

2- The Envelope

The virion envelope, usually made of lipids, proteins, and glycoproteins, is derived from the host cell membrane
Glycoproteins (projections) play a role in attachment.

Note:* This is a summary of the provided text. Some details, particularly specific examples, were omitted for brevity and conciseness. Please be sure to consult the original source material or use separate study notes from videos or articles for a complete understanding.

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Description

Test your knowledge on arboviruses and their impacts on human health. This quiz covers key concepts about mosquito and tick-borne viruses, clinical syndromes like yellow fever, and classifications of hepatitis C viruses. Challenge yourself with questions on flavivirus structure and characteristics of dengue hemorrhagic fever.