Virology Flashcards
Describe the characteristics of viruses.
Small size
Simple chemical composition
- no intracellular organelles
DNA (Herpes) or RNA (mumps).
Describe the key stages of viral replication in a Herpes Simplex virus.
Binding
Entry
Release and nuclear transport
Nuclear entry
Gene expression
DNA replication
Packaging
Egress
If you suspect an intra-oral viral infection, what special investigations might you do?
Intra-oral swab of the area
- flocked swab.
- Place in a molecular sample solution and after immersion remove the swab.
What should you include in your virology request form?
Pt details- Name, DOB, CHI number, address.
Your details, practice address and contact number of practice.
Clinical details- history and examination, provisional diagnosis.
Specify test- serology, PCR.
Describe the Pathogenesis of HSV.
Acute infection- binding, entry, nuclear transport, nuclear entry, gene expression, DNA replication, packaging, egress.
Latency- Virus then becomes latent in peripheral nerves- in the head and neck usually the trigeminal nerve.
- retrograde transpot.
Reactivation of the virus occurs- anterograde transport from the nerve back into the tissues.
- herpes labialis, recurrent gingivostomatitis.
What is the reservoir and route of transmission of HSV?
Reservoir- saliva
Route of transmission- direct by close person to person contact.
If a patient presents with HSV infection, what would you do?
In the first instance- advise the pt to stay hydrated, soft diet, prescribe chlorhexidine mouthwash 2% 300ml and use this twice per day for 4 minutes.
Can also prescribe hydrogen peroxide 6%, 300ml.
For Herpes Labialis- prescribe topical Acyclovir cream 5%, 2g.
Systemic acyclovir- 200mg, 25 tablets, 1 tablet 5 times per day for 5 days.
What are the complications of varicella zoster virus?
Secondary bacterial infection
Post-herpetic neuralgia
Ophthalmic zoster
Ramsay hunt Syndrome
What are the signs and symptoms of Zoster virus?
Vesicles appear in dermatome, representing cranial or spinal ganglia where the virus has been dormant.
Will not cross the midline
Affected area may be painful
Associated paraesthesia
Ocular involvement
How is Varicella and Zoster commonly transmitted?
Varicella- contact with the virus
- vesicle fluid is infectious.
Zoster- latent virus in sensory ganglion.
- vesicle fluid not usually transmissible.
What type of patients does varcicella and zoster typically affect?
Varicella- children (chickenpox)
Zoster- elderly and immunocompromised
What is the treatment for Shingles (varicella Zoster virus)?
Systemic Aciclovir- 800mg tablets, 35 tablets, 1 tablet 5 times per day for 7 days.
What is Acyclovir?
Acyclic Purine Nucleoside.
What is the mechanism of action of Acyclovir?
Acyclovir is converted to acyclovir trisphophate by addition of phosphate groups by viral enzymes (thymidine kinase).
- viral thymidine kinase has a higher affinity for acyclovir.
The aciclozir triphosphate is incorporated into the growing DNA strand- halts further elongation of the DNA molecule and stops viral replication.
- acyclovir triphosphate is a better substrate for viral than for host cell DNA polymerase.
Can resistance to acyclovir occur?
Yes, due to mutations in viral thymidine kinase.
