viruses Flashcards
Describe a viruses size
- 20-300nm
- visualised under electron microscopy
What shapes do viruses usually have?
- icosahedral
- helical
Which characteristic of viruses make it use the host cellular machinery to replicate?
they are obligate intracellular parasites
Describe the capsid of a virus
protein coat that encloses genome and core proteins
Describe the envelope of a virus
- lipid bilayer that surrounds capsid of SOME viruses
- it contains glycoproteins that form projections
Describe the genome of a virus?
- either DNA or RNA
What are the different person-to-person HORIZONTAL transmission routes for viral infections?
- airborne
- fecal-oral
- sexual
- vector-borne
- blood
What is the VERTICAL transmission route for viral infections?
from mother to child
What is pathogenesis?
study of the disease process
What is invasiveness?
the capacity of a virus to enter a tissue or organ
What is tropism ?
ability of different viruses to infect different cell types
What is virulence?
the ability for a virus to cause disease
What are the methods for viral diagnosis?
- direct detection
- indirect detection
Describe direct detection of viruses?
- detection of the whole virus or parts of it
Describe indirect detention of viruses?
- detection of human antibodies against the virus
What are the possible outcomes of acute viral infections?
- complete resolution and recovery (clearance of virus from the host)
- chronic infection (persistance of virus in the host)
What are the types of chronic viral infection?
- continuous viral replication
- latency and reactivation
- invasion of genome followed by vertical transmission
What is latency?
a unique transcription and translational status of a virus in which the productive replication cycle is silent but can reinitiate
Describe continuous viral replication
- continuous generation of infective virions (e.g HIV)
What are the ways to prevent airbone viral transmission?
- active immunisation (vaccines)
- masks
- social distancing
- quarantine
- hand washing
What are the ways to prevent fecal-oral viral transmission?
- active immunisation (vaccines)
- safe water supply
- safe disposal excreta
- avoid raw food
- hand washing
What are the ways to prevent HIV infection?
- treatment as prevention (TasP)
- pre-exposure prophylaxis (PrEP)
- post exposure prophylaxis after sexual exposure (PEPSE)
- condoms
- male circumcision
What are the steps of viral replication?
- Binding between virus and target cell (attachment)
- Penetration of virus into host
- Enzymatic removal of protein coat and liberation of viral nucleic acid into cytoplasm
- Production of viral specific mRNA
- Morphogenesis and maturation of new viruses
- Release
What are cytopathic effects?
visible changes/damage to host cells due to viral infection
