Viruses Flashcards
Describe characteristics of viruses?
Small Structure can either be : Icosahedral - 20 faces of equilateral triangles. Helical - protein binds around DNA/RNA. Or Complex. Can only replicate within a host Non-cellular Protein capsule to protect DNA.
How can viruses be classified?
Virion shape / symmetry
Presence / absence of envelope
Genome structure
Mode of replication
What are some common routes for viral infection?
Blood borne Sexually transmitted Vertical (mother to baby) Faecal - oral Droplet Airborne Close contact Vector borne (often mosquitos) Zoonotic (animal host)
Give some examples of viruses that only infect humans?
Small pox
Measles
What is a novel virus?
An unseen before virus that has other been isolated from its own reservoir or isolated as the result of spread to an animal or human host where the virus had not been identified before.
What may lead to new strain of virus being produced?
Coinfection of human and animal or bird strains in one organism may lead to recombination and generation of a new strain.
What is viral latency?
The reactivation of virus cells that have lain dormant within the host cells since the primary infection.
What can increase viral latency?
Someone who is immunocompromised.
In what way can a virus be detected?
Whole organism
Part of the organism - antigen, nucleic acid
Immune response to a pathogen - antibodies
Describe some methods of preventing viral infection?
Immunisation - vaccination, passive immunisation with immunoglobulin. Prophylactic treatment post exposure Isolation of symptomatic patients PPE Safe use and disposal of sharps Screening
What properties do viruses that can potentially be eradicated have?
No animal reservoir or ability to amplify in the environment
Clearly identifiable, with accurate diagnostic tool
No chronic carrier state
Efficient and practical intervention, e.g. vaccination
Political / social support
What are some examples of viruses that have the potential to be eradicated?
Small pox (eradicated in 1979)
Measles
Polio
What are the different types off virus pathogenic mechanisms?
Cell destruction following virus infection
Virus-induced changes to cellular gene expression
Immunopathogenic disease
Where are the sites of viral entry on the body?
Respiratory tract Alimentary tract Urinogenital tract Skin Capillary Arthropod Conjunctiva
What is an acute infection?
Happens once in a localised specific site. E.g influenza
What is a latent infection?
Virus stays in body after first acute infection and reoccurs. e.g herpes.
What is a chronic infection?
Virus is always present in the blood. Continually exists but at low levels.
What are the effects of influenza virus?
Virus infects cells of the respiratory tract
Destruction of respiratory epithelium
Secondary bacterial infections due to the changing of antigenic markers.
Altered cytokine expression leading to fever.
What is antigenic drift?
Minor changes (natural mutations) in genes of flu viruses, occurs gradually over time to generate antigenic variants. Slow change.
What is antigenic shift?
Abrupt major changes in virus antigenic structure.
What are some characteristics of enterovirus infections?
70+ known
Arrives in the body through the gut.
Can lead to viraemia - if neuronal may cause paralysis.
E.g polio
What are the main steps of the retrovirus replication cycle?
Attachment of virus Membrane fusion Uncoat and unwind viral RNA Viral DNA replaces human DNA Leads to tumour formation.
