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Questions and Answers
What is the main function of viral proteins in a virus?
What is the main function of viral proteins in a virus?
What is the primary function of hemagglutinin in viruses?
What is the primary function of hemagglutinin in viruses?
What is the characteristic of viral nucleic acid that is used for classifying viruses into families?
What is the characteristic of viral nucleic acid that is used for classifying viruses into families?
What is the term for the 'core' or 'genome' of a virus?
What is the term for the 'core' or 'genome' of a virus?
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What is the characteristic of lipid-containing viruses?
What is the characteristic of lipid-containing viruses?
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What is the term for the symmetry of viruses with a polygon with 12 corners/vertices, 20 surfaces/sides?
What is the term for the symmetry of viruses with a polygon with 12 corners/vertices, 20 surfaces/sides?
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What is the term for the symmetry of viruses with protein subunits (capsomeres) packed in a helical array around the viral nucleic acid?
What is the term for the symmetry of viruses with protein subunits (capsomeres) packed in a helical array around the viral nucleic acid?
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What is the main function of the viral lipid envelope?
What is the main function of the viral lipid envelope?
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Which of the following viruses causes most epidemics and all global pandemics?
Which of the following viruses causes most epidemics and all global pandemics?
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What is the natural reservoir of SARS-like coronaviruses?
What is the natural reservoir of SARS-like coronaviruses?
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Which of the following viruses is characterized by causing common colds but can also cause serious respiratory illness?
Which of the following viruses is characterized by causing common colds but can also cause serious respiratory illness?
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What is a common symptom of parvovirus B19 infection?
What is a common symptom of parvovirus B19 infection?
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What is the type of RNA found in Orthomyxoviruses?
What is the type of RNA found in Orthomyxoviruses?
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Where do most RNA viruses replicate?
Where do most RNA viruses replicate?
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Which of the following viruses is implicated in gastroenteritis in infants?
Which of the following viruses is implicated in gastroenteritis in infants?
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What is the main route of transmission for poliovirus?
What is the main route of transmission for poliovirus?
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What is the likely origin of the SARS virus?
What is the likely origin of the SARS virus?
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What is the result of destruction of motor neurons in the spinal cord in poliovirus infection?
What is the result of destruction of motor neurons in the spinal cord in poliovirus infection?
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What is the purpose of vaccination against poliovirus?
What is the purpose of vaccination against poliovirus?
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What is the most common form of poliovirus infection?
What is the most common form of poliovirus infection?
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What is the duration of nonparalytic poliomyelitis (Aseptic Meningitis)?
What is the duration of nonparalytic poliomyelitis (Aseptic Meningitis)?
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What is the outcome of a small percentage of cases of nonparalytic poliomyelitis?
What is the outcome of a small percentage of cases of nonparalytic poliomyelitis?
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What is the result of HIV infecting T-Helper Cells?
What is the result of HIV infecting T-Helper Cells?
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What enables extremely virulent strains of viruses to evolve?
What enables extremely virulent strains of viruses to evolve?
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What is characteristic of Herpesviruses?
What is characteristic of Herpesviruses?
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What is the sequence of events following an initial Herpesvirus infection?
What is the sequence of events following an initial Herpesvirus infection?
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What is a common source of Herpesviruses transmission?
What is a common source of Herpesviruses transmission?
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What is a complication of HSV-1 infection?
What is a complication of HSV-1 infection?
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What is the route of transmission for HSV-2?
What is the route of transmission for HSV-2?
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What is a possible consequence of oral to genital sex with HSV-1 positive individuals?
What is a possible consequence of oral to genital sex with HSV-1 positive individuals?
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What is the most common fungal bloodstream infection in hospitalized patients?
What is the most common fungal bloodstream infection in hospitalized patients?
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Which of the following is a characteristic of Cryptococcosis?
Which of the following is a characteristic of Cryptococcosis?
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What is the mode of transmission of Cryptococcosis?
What is the mode of transmission of Cryptococcosis?
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What is the primary site of infection in Dermatophytosis?
What is the primary site of infection in Dermatophytosis?
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What is the term for the presence of Candida species in the blood?
What is the term for the presence of Candida species in the blood?
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Which type of mycosis is caused by dimorphic fungi?
Which type of mycosis is caused by dimorphic fungi?
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What is the term for fungal infections that invade the deep organs?
What is the term for fungal infections that invade the deep organs?
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Which of the following is a characteristic of Candidemia?
Which of the following is a characteristic of Candidemia?
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Study Notes
Viral Structure and Composition
- A virion is an intact infectious virus particle, consisting of viral protein, nucleic acid, and lipid envelopes.
- Hemagglutinin is a naturally occurring glycoprotein that causes red blood cells to agglutinate or clump together.
- Viral protein facilitates the transfer of viral nucleic acid from one host cell to another, protects the viral genome against inactivation by nucleases, and participates in the attachment of the virus particle to a susceptible cell.
- There are two types of viral proteins: structural proteins present in the coat of the virus, and non-structural proteins, including hemagglutinin and enzymes.
Viral Nucleic Acid
- Viruses contain a single kind of nucleic acid, either DNA or RNA, which encodes the genetic information necessary for replication.
- The genome may be single or double-stranded, circular or linear, and segmented or non-segmented.
- The type of nucleic acid, its polarity, and its size are major characteristics used for classifying viruses into families.
Viral Lipid Envelopes
- Lipid is acquired when the viral nucleocapsid buds through a cellular membrane during maturation.
- Lipid-containing viruses are sensitive to treatment with ether and other organic solvents, indicating that disruption or loss of lipid results in loss of infectivity.
- Nonlipid-containing viruses are generally resistant to ether and detergents.
Symmetry of Viruses
- Icosahedral viruses have a rigid, polygon-shaped structure with 12 corners/vertices and 20 surfaces/sides.
- Examples of icosahedral viruses include herpesvirus, parvovirus, papovavirus, adenovirus, picornavirus, and reovirus.
- Enveloped/helical viruses have protein subunits (capsomeres) packed in a helical array around the viral nucleic acid, forming a spiral tube or helix.
- Complex viruses neither have icosahedral nor enveloped/helical structures.
Virulence Factors
- Some viral particles can replicate during the defensive inflammation responses of the host, such as during virus-induced fever.
- Extremely virulent strains can eventually evolve by mutation and natural selection within the virus population inside a host.
DNA Viruses: Herpesviruses
- Herpesviruses are enveloped, large viruses with a double-stranded DNA genome, belonging to the family Herpesviridae.
- Sources of herpesviruses include saliva, skin lesions, and respiratory secretions from infected, asymptomatic carriers.
- Herpesviruses produce an initial acute infection followed by a period of latent infection, with reactivation resulting in recurrent infection.
- Herpesviruses exhibit a wide spectrum of disease, including gingivostomatitis, pharyngitis or tonsillitis, lesion on the face, herpes encephalitis, and eczema.
RNA Viruses
- RNA viruses replicate in the cytoplasm and have a simpler mechanism of replication, with early and late mRNA not clearly separated.
- There is no host cell RNA polymerase that can use the viral parental RNA as a template for synthesis of complementary RNA strands.
- Examples of RNA viruses include enteroviruses, polioviruses, coronaviruses, and orthomyxoviruses.
Enteroviruses
- Enteroviruses are transient inhabitants of the human alimentary tract and may be isolated from the throat or lower intestine.
Polioviruses
- Polioviruses are shed by infected individuals into the environment, spreading rapidly in areas of poor sanitation.
- Poliovirus causes polio or poliomyelitis, entering through the mouth and multiplying in the intestine.
- The virus mainly affects nerves in the spinal cord or brain stem, resulting in flaccid paralysis.
- Prevention and control are achieved through a series of vaccinations.
Arboviruses in the Philippines
- Examples of prevalent arboviruses in the Philippines include dengue (DEN), Japanese encephalitis (JE), chikungunya (CHIKV), and Zika virus (ZKV).
Coronaviruses
- Coronaviruses are large, enveloped RNA viruses that cause common colds and may cause lower respiratory tract infections and gastroenteritis in infants.
- Novel coronaviruses have been identified as the cause of severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS).
Fungal Infections
- Yeast infections, such as candidemia, can spread through eyes, endocardium, meninges, kidney, liver, spleen, and bone, and may cause cross-infection (mother to baby).
- Diagnosis is through blood culture test.
- Cryptococcosis is a fungal infection caused by Cryptococcus neoformans, which is found worldwide and is an opportunistic invasive fungus.
Clinical Classification of Mycoses
- Superficial mycoses affect the mucus membrane or keratinized tissue.
- Subcutaneous mycoses are due to the implantation of environmental fungi.
- Systemic mycoses cause widespread disease and are serious and fatal, often affecting healthy individuals and opportunistic infections in immunocompromised individuals.
Filamentous Fungi Infections
- Examples of filamentous fungi infections include dermatophytosis (ringworm infection), which appears as red patches on the affected area of the skin and later spreads to other parts of the body.
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Description
This quiz covers the composition and properties of viruses, including their chemical makeup, proteins, and mechanisms of infection. Test your knowledge of viral structure and function!