Essentials Of Virology I Flashcards
What is a virus?
An infective agent that typically consists of a Nucleic acid molecule in a protein coat, is too small to be seen by a light microscope and is able to multiply only within the living cells of a host
How many viruses are there that infect mammals?
320,000 ish but constantly changing
What are the four (ish) viral hosts?
Humans
Animals (and insects hence the ish)
Plants
Bacteria
What does it mean if viruses move between hosts?
They move between humans and animals for example
What is a host range?
Where a virus can be found
What is a reservoir or an amplifying host?
Animals where the virus replicates but doesn’t cause disease
What are the three major categories of reservoir hosts?
Avians, swine and rhodentia
What is one of the most common ways animal to human transmission happens?
Through vectors (insects)
Why don’t viruses infect the vectors?
The insects immune system is very complex
What is horizontal transmission?
Between the same species
What is vertical transmission?
From mother to child
What is a dead end host?
A host which gets infected with the virus but doesn’t do anything with it (the virus ‘dies’ with the host)
What is a viruses tissue tropism?
Tissues that viruses can be found in
Through evolution, what do viruses replicate to do?
Replicate in tissues that favour transmission between hosts and allow themselves to evade the immune system of the host
How do viruses cause disease directly?
As a product of their host range and tissue tropism (replication killing cells)
How do viruses cause disease indirectly?
By promoting or inhibiting cell function
What types of disease can viruses cause in humans?
Cancer, immunodeficiency and respiratory
What does acute disease mean?
Virus makes you sick very quickly and then leaves
What does chronic disease mean?
Disease develops/comes on really slowly
What are prions?
Proteins that do not contain Nucleic acid and replicate inside cells
Why don’t antibiotics work on viruses?
Generally they target cell wall synthesis and viruses dont have a cell wall
What is an obligate intracellular parasite?
A virus
What can the virus structure determine?
Host range and tissue tropism
How do viruses enter a cell?
Direct fusion or endocytosis
How do viruses move inside the cell?
Using intracellular structures
How do viruses exit from the cell?
Budding or lysis
What are the 5 essential steps in virus replication?
- Entry into the cell
- Genome movement
- genome replication
- genome packaging into protein shells
- exit from the cell
