L1/2: Basis of infection Flashcards
What are the biosafety risk groups?
BSL1 to BSL4 - 1 being low risk and 4 being high risk
What factors influence a viruses biosafety level? (5)
- pathogenicity
- infectious dose
- mode of transmission
- host range
- availability of preventative measures
Give 2 examples of viruses for each BSL.
BSL1 = E. coli, Baculovirus, Infectious canine hepatitis virus
BSL2 = hepatitis viruses, human herpesvirus, Influenza, pox viruses (except variola), measles
BSL3 = SARS, Hantavirus, Yellow fever, Rabies, HPAI viruses, Japanese encephalitis virus, HIV (when culturing large quantities, otherwise BSL2)
BSL4 = Ebola, Variola (smallpox), monkey pox, Hendra virus, Nipah virus, Herpes B virus
What are the four determinants of viral tropism?
- susceptibility
- permissivity (TFs, degree of differentiation, temp)
- accessibility
- defence
What is viral tropism?
The extent to which a virus can infect its host. Broad tropism refers to the viruses ability to infect many tissues and cell types.
Eg. Rabies infects primarily neuronal tissue
What is the difference between primary and secondary virus replication
Primary replication occurs after initially gaining entry into the host while secondary replication involves other tissues/organs/cell types, usually after systemic spread.
What are the 6 steps of a virus life cycle within a cell?
- Attachment/absorption
- Penetration
- Uncoating
- Replication
- Assembly
- Release
What is viral pathogenesis?
The process by which infection leads to disease
What influences viral pathogenesis? (8)
- transmission/entry
- primary replication site
- mode of spread throughout host
- target organs/tissues
- mechanism of tissue damage
- host response
- ability of host to clear infection (transient vs persistent)
- virulence
How do viruses typically spread to the bloodstream?
Through the basement membrane of epithelial cells
