Questions and Answers
What is the primary function of the capsid in a virus?
To protect the viral genome from inactivation by nucleases
What is unique about the genetic material of a virus?
It can be either DNA or RNA, but not both
What is the role of the viral attachment protein (VAP)?
To attach the virus particle to a target cell by interacting with a specific cellular receptor
What is the characteristic of viruses that makes them obligate intracellular organisms?
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What is the function of the nucleic acid in a virus?
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What is the characteristic of the protein coat that surrounds the nucleic acid genome?
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What is the process called when a virus acquires its envelope from the infected cell?
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Which of the following viruses is primarily transmitted through faecal-oral transmission?
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What is the term for the characteristic changes observed in cells infected with viruses?
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Which of the following is NOT a common route of viral transmission?
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What is the term for the process of cultivating viruses in the laboratory using animal cells?
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Which of the following viruses is commonly associated with respiratory tract infections?
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What is the term for the study of the immune response to viral infections?
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Which of the following is a common method of diagnosing viral diseases?
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Which of the following viruses is primarily associated with epidemic outbreaks of gastroenteritis and can be transmitted through contaminated foods?
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What is the primary mode of transmission for Hand, Foot, and Mouth Disease?
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Which of the following viruses can cause life-threatening respiratory paralysis?
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What is the primary method of diagnosis for Hepatitis A Virus?
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Which of the following vaccines is an inactivated vaccine administered through IM injection?
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What is the primary mode of transmission for Poliovirus?
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What is the primary treatment for Poliovirus infection?
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Which of the following viruses can cause a mild febrile illness lasting a few days, accompanied by headache and vomiting?
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Study Notes
Viruses
- Smallest infectious agents (20-300nm)
- Obligate intracellular organisms, dependent on host cell for energy metabolism and synthesis of macromolecules
- Contain either DNA or RNA as genetic material, never both
- Surrounded by protein coat and sometimes a lipid- and glycoprotein-containing envelope
Basic Virus Structure
- Nucleic acid carries genetic specificity to code for all virus-specific macro molecules
- Capsid is a symmetric protein shell that encloses the nucleic acid genome
- Composed of structural units (capsomers) visible in electron microscope
- Functions: protect viral genome, determine antigenic characteristics, and responsible for structural symmetry
Envelope and Symmetry
- Envelope is a lipid-containing membrane that surrounds some virus particles, acquired from infected cell through "budding off" process
- Types of symmetry: Adeno viruses, Herpes viruses, MYXO viruses, RHABDO viruses, and Poxvirus
Viral Life Cycle
- Six stages within host cell: Adsorption, Penetration, Uncoating, Macromolecular synthesis, Assembly, and Release
Cultivation of Viruses
- Three common tissue cultures: Chicken egg culture, Cell culture, and Animal inoculation
Cytopathic Effects
- Changes in size and shape, cytoplasmic inclusion bodies, nuclear inclusion bodies, cells fuse to form multi-nucleated cells, cell lysis, altered DNA, and transformation into cancerous cells
Diagnosis of Viral Diseases
- Clinical picture, cell culture, viral antigen, and antibodies
- Screening for immune response to virus
Transmission of Viruses
- Respiratory transmission: Influenza A virus
- Faecal-oral transmission: Enterovirus
- Blood-borne transmission: Hepatitis B virus
- Sexual transmission: HIV
- Animal or insect vectors: Rabies virus and ARBO viruses
Respiratory Tract Infections
- Adenoviruses: Adenoiditis, Pharyngitis, and Bronchopneumonitis
- Cytomegalovirus: Interstitial pneumonitis
- Varicella-zoster virus: Pneumonitis
- Enteroviruses: Coxsackie B, ECHO
- Rhinoviruses: Common cold
- Coronaviruses: Common cold
- Influenza viruses: Influenza (upper and lower respiratory tract infections)
- Parainfluenza viruses: Parainfluenza (laryngitis, tracheitis)
- Respiratory syncytial virus: Bronchopneumonitis
Gastrointestinal Infections
- Norwalk-like viruses (caliciviruses): epidemic outbreaks of gastroenteritis, associated with consumption of contaminated foods and aerosol spread
- Hepatitis A virus: Infective hepatitis, transmitted through contaminated foods, causing fever, anorexia, nausea, vomiting, jaundice, and dark urine
- Poliovirus: causes poliomyelitis, three antigenically distinct types, transmitted through fecal-oral route and close personal contact
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