Immunology - Virology

Question 1

Methods of virus transmission

Answer 1

1. Aerosol transmission
   Spread via respiratory droplets
   Droplets remain airborne for days
   Scaling generates lots of aerosol → impt to identify infectious patients
   Influenza A, Strep A
2. Blood-borne transmission
   Exposure to infectious bodily fluid via oral mucosa or broken skin
   Unsterilised instruments
   Hep B, C, HIV
3. Faecal-Oral transmission
   Faecal-contaminated water source
   Natural disasters - hurricanes, floods
   Agricultural practices
   Inadequate hygiene when preparing food, food prep in presence of faeces
   Houseflies
   Polio
4. Insect vectors (eg zika virus)
   Mosquitoes, animals
   Rabies, Zika, Ross River fever

Question 2

Virulence / Mechanisms of pathogenicity

Methods of entry

Answer 2

AIGE:
Attachment to host - spike protein (HA/NA on influenza) on virus binds to receptor on host cell, which triggers viral entry into cell
Invasion of host
Growth and colonisation - proliferation

Evasion of destruction by host
Exotoxins
Endotoxins
Quorum sensing

Question 3

Potential occupational hazards of virus transmission in the dental surgery

Answer 3

Aerosols
Contact - Contaminated surfaces (fomites)
Eg doorknobs, dental equipment, mobile devices, fabric, pens, magazines
Non-porous, smooth surfaces transmit pathogens better than porous materials (which absorb and trap contagion)

Question 4

Virus structural vulnerabilities

Answer 4

Enveloped viruses - target the lipid viral envelope
Lipid envelopes are quite fragile and sensitive to denaturation by heat and pH change.
Lipid solvents (detergent), pH/temp (autoclave), alcohol sanitisers (disrupt envelope killing the virus), chemicals and desiccation are more effective

Non-enveloped/naked viruses are more resistant to environmental conditions - heat/pH change, chemicals. More virulent, cannot be killed by sanitisers

Question 5

Antiviral targets

Answer 5

1) Attachment/entry
- Anti-hemagglutinin - binds to sialic acid to prevent binding of hemagglutinin on influenza virus
2) Nucleic acid replication
- Virus polymerase inhibitors
3) Viral protein processing
- Anti-neuraminidase is an enzyme inhibitor prevents dvpt of viral proteins → non-functional virus
4) Viral maturation
- Neuraminidase inhibitor

Question 6

Antibiotic resistance

Answer 6

Changing target site so antibiotic cannot bind
Enzymes that inactivate drug
Beta-lactamase
Upregulating pumps for removal of drug

Question 7

Patient risks, practitioner risks

Answer 7

Health implications
Impacts on quality of life
Not being able to work
Loss of income
Transmission to other patients, staff, that may be immunocompromised

Question 8

Prevention strategies
Gold standards

Answer 8

1) Avoidance of exposure
Protection
Barrier utilities - aerosols and vapour hazards: Gloves, gowns, protective eyewear, masks and respirators, high power suction, good ventilation
2) Immunisation
Vaccination
3) Post-exposure prophylaxis
Hand hygiene