VIROLOGY- INTRO Flashcards
A submicroscopic, obligate intracellular parasite, among the smallest of all infectious agents, capable of infecting any animal, plant, or bacterial cell.
virus
What is essential for the survival of viral infectious agents?
Their ability to infect and reside in a living organism.
Where are viruses found?
In every ecosystem.
Can viruses replicate without a living host cell?
No, they are strict obligate intracellular parasites and cannot replicate without a living host cell.
Major changes in viral genomes that result in novel viral antigens.
antigenic shift
The specificity of virus types, where each virus has a limited number of hosts it can infect.
viral tropism
The emergence of a new viral disease across a very large geographic region (worldwide) with prolonged human-to-human transmission.
Pandemic
Minor changes in viral genomes that occur infrequently.
antigenic drift
What is the term for a virus that emerges as a completely new entity?
A completely new or “novel” virus.
What are the two or three parts that make up a virus particle (virion)?
-Inner nucleic acid core (RNA or DNA)
-Protein coat (capsid)
-Lipid-containing envelope (in some larger viruses)
It surrounds and protects the nucleic acid.
protein coat (capsid)
How are enveloped viruses typically transmitted?
By direct contact: respiratory, sexual, or parenteral contact.
Why are “naked” viruses resistant to environmental factors?
Because they do not have an envelope, making them very stable.
are extensions from the surface of the virus.
glycoprotein spikes
The nucleic acid genome surrounded by a symmetric protein coat.
nucleocapsid
It encodes the proteins required for viral penetration, transmission, and replication.
Nucleic acid genome
What determines the mechanism for viral replication?
The structure of the viral genome (e.g., (+) sense-strand RNA, (–) sense-strand RNA, and DNA genomes).
protects the viral genome and is responsible for the tropism to specific cell types in naked viruses.
Viral capsid
It is responsible for viral entry into the host cell.
lipid envelope
It lies between the envelope and the nucleocapsid and may have enzymatic activities or biological functions related to infection, such as inhibition of host-cell transcription
Matrix protein
very susceptible to drying and destruction in the environment
Enveloped viruses
Typically are composed of repeating structural subunits referred to as?
Capsomeres
Because of their stability, they are typically transmitted by the fecal-oral route
“Naked” viruses
What factors influence specimen selection for viral detection?
The specific disease syndrome, viral agents suspected, and time of year.
When should specimens for viral detection be collected?
As early as possible after the onset of symptomatic disease.
How can the recovery and detection of viral agents be enhanced?
By using validated devices or containers.
Which type of specimen is superior for recovering viruses: nasopharyngeal aspirates, throat swabs, or nasopharyngeal swabs?
Nasopharyngeal aspirates.
For which viruses are throat swabs acceptable for recovery?
Enteroviruses, adenoviruses, and HSV.
Which specimens are preferred for the detection of RSV, influenza, and parainfluenza viruses?
Nasopharyngeal swab or aspirate specimens.
Are all respiratory specimens acceptable for culture of most viruses?
Yes,all respiratory specimens are acceptable for culture of most viruses.
What specimens are excellent for detecting viruses that infect the lower respiratory tract?
Washings and lavage fluid collected during bronchoscopy.
Which viruses are especially detected using bronchial and bronchoalveolar washes?
Influenza viruses and adenoviruses