Virus Structure and Transmission Flashcards
What is the general structure of a virus
DNA/RNA genome (can be DS, SS, linear or circular), surface protein, capsid protein and envelope
What are the characteristics of viruses
Obligate intracellular parasites that can only grow in appropriate host cells
What are virions
Purified virus particles that are much simpler in construction and content than any cell from any organism (simplest life form)
What is the role of the virus genome
Encode viral proteins
What do virions contain
Numerous copies of one or more different proteins and one nucleic acid molecule (which is the virus genome)
What is the capsid
A protein shell made up of identical caposomeres the virus genome is enclosed
What is the nucleocapsid
The name given to the genome enclosed by the capsid
Describe the envelope
Lipid membranes which are derived from host cell but also contain virus-coded proteins which many viruses are enclosed in
What are the two types of naked viruses (no envelope)
Naked icosahedral (football shape) and naked helical (helical shape)
Are there any human viruses with the naked helical structure
No
What are the two types of enveloped virus
Enveloped icosahedral and enveloped helical
What are the 5 main types of virus
Complex, enveloped icosahedral, enveloped helical, naked icosahedral and naked helical
What are the benefits of oncolytic viruses
Can be used to treat cancer
Describe the virus cycle of infection
Transmission- entry - primary site replication- spread within host - shedding- transmission
How can we control virus infection
By breaking virus cycle of infection
What are the 3 modes of virus transmission
Horizontal transmission, vertical transmission and zoonosis
What is horizontal transmission
Virus transmission from person to person
What is vertical transmission
Virus transmission from mother to baby
What is zoonosis
Virus transmission from animal to man
What are the most common routes of horizontal transmission
Respiratory and faecal-oral
How to viruses spread by respiratory transmission
- direct inhalation of droplets
- droplets may infect conjunvpctiva
- droplets may fall onto surfaces and be transferred by fingers to mouth, nose or conjunctiva
- droplet may be be desiccated
What is important for determining route of transmission
Droplet size
What are examples of horizontal transmission
Respiratory, faecal-oral, mechanical e.g. blood transfer , sexual, urine
Describe vertical transmission
Can be primary infection of mother while pregnant or reactivation of a persistent infection that is transferred to child via transplacental, during or after birth (breast milk)
