Intro To Viruses Flashcards
What is a virus?
A non-cellular genetic element that cannot replacing independently of the host
Most viruses have a specific host-range
What are the defining chaRACTERISTICS OF VIRUSES?
VIRION SHAPE/SYMMETRY
Presence/absence of ‘envelope’
Genome structure
Mode of replication
Examples of blood-bourne viruses
HIV
Hep B
Hep C
Examples of sexually transmitted viruses
HIV
Hep B
Examples of faecal-orally transmitted viruses?
Hep A Hep E
Polio
Examples of Droplet transmitted viruses
Influenza
RSV
What is RSV?
Respiratory syncytial virus
Causes respiratory tract infections
Examples of airborne viruses?
Measles
Chickenpox
Examples of close contact viruses?
Herpes
Examples of vector borne viruses?
Dengue
Yellow fever
Chikungunya
Examples of zoonotic viruses
Rabies
MERS
Ebola
Describe structure of virus
Nuclei acid with associated polymerase
Encased in protein capsid, encased by lipid envelope, with spike projections.
How does a virus replicate?
Attaches self to host cell and injects genetic material
Budding and release
Maturation
Attachment
Host range?
Some viruses only infect humans (small pox, measles)
Some also infect animals
- co-infection of of human and animal/bird strain in one organism can lead to generation of a new strain
What can lead to the generation of a new strain?
Co infection of human and animal/bird strains in same organism.
Consequences of viral infection?
Clearance - Hep C (no lasting immunity)
Measles (long term immunity
Chronic infection
LAtent infection
Transformation (long-term with altered cellular gene expression)
What is viral latency
Following primary infection, viruses lie dormant.
Genome retained in host cell, but expression restricted, few viral antigens produces.
Reactivation is more likely to occur and is more severe in immunocompromised patients.
What is more likely to occur in immunocompromised patients?
Reactivation (viral latency
What is the link of cancer and viruses?
Number of infections can lead to cancer
Mechanisms altered:
Modulation of cell cycle (proliferates cell proliferation)
Modulation of apoptosis /9prevention of programmed cell death)
Oxygen species mediate damage
What are virustatic antiviral agents?
Stop replication but do not KILL virus
What does virustatic mean?
Stops virus replicating but does not kill virus
What does virucidal mean?
Kills the virus
Anti viral therapy
Side effects common (toxicity to host cell)
Only used in minority of viral infections
What is prophaxis?
Prevents infection
What’s pre-emptive therapy?
When evidence of infection/replication is detected, but symptoms are not yet apparent.
What is suppressive therapy?
Keeps viral replication below rate that causes tissue damage in asymptomatic but infected patient.
What are ways of preventing viruses?
Immunisation (vaccination, or passive immunisation with immunoglobulin)
Prophylactic treatment post exposure (prevents infection)
Infection prevention/ control measure - e.g isolation of patient, personal protective equipment, disposal of sharp objects.
What is antenatal screening?
Screening during pregnancy
What are infection prevention examples?
Isolation of symptomatic patients,
Personal protective equipment
Disposal of sharp objects
What kind of screening is used in viruses?
Blood
Tissue
Organ screening
Antenatal screening
What characteristics of viruses mean that they could potentially be eradicated?
No animal reservoir/ ability to amplify in environment.
Clearly identifiable/ diagnosed
No chronic carrier state
Efficient and practical intervention (vaccination)
Political/social support
What is a virus that has been eradicated?
Smallpox
Next virus to be eradicated?
Polio
