Viruses

Question 1

Why are viruses important in oral health

Answer 1

Cause infection in oral cavity
Easily spread
Hard to treat

Question 2

Draw the structure of a virus

Answer 2

4 parts - capsid ( protein case )
- nucleic acid genome (DNA OR RNA -not both )
- envelope (lipid membrane - helps adhere to host cell)-NOT ALL VIRUSES HAVE

Lack organelles /enzymes

Question 3

What is special regarding virus replication

Answer 3

Cannot reproduce themselves or use binary fusion
Must use another host cell to replicate

Question 4

Name 5 steps in virus replication

Answer 4

1. Recognise a host cell receptor and Attachment to host cell -
2. Absorbing into cell - 3 ways
   - fusing of virus and host cell membrane
   - endocytosis of virus
   - diffusion entire virus across the host cell
   membrane
3. Nucleic acid replication - particles reach cytoplasm capsid sheds off and genome uses the host cells “machinery “to replicate viral genome into viral proteins ( via transcription/translation )
4. Viral assembly - new viral proteins/genomes assemble into new viral particles
5. Virus release - 3 mechanisms
   - cell lysis -releases virus OR
   if enveloped viruses -bud or exocytosis where the protein inserts itself into the host membrane

Question 5

What is viral latency

Answer 5

After the primary infection the virus can lay “dormant” in a ganglion then become reactivated and cause active secondary infection

Question 6

Give an example of a mouth virus and how it presents on its primary then secondary infection once its been latent

Answer 6

Herpes simplex virus type 1(most common mouth viral infection )
see. Primary stage - gingivostomatitis - asymptomatic or ulcers then it can …

Moves to trigeminal ganglion and lays in latent stage

Reactivation by stress/ sunlight /illness/ Trauma area etc

Reactivates - secondary HSV - cold sore - travels down peripheral nerve of trigeminal Nerve and causes ulceration on mucocutaneous area lip

Question 7

What can cause reactivation of secondary virus infection in latent state

Answer 7

Stress
Sunlight
menstruation
illness
Trauma to the area

Question 8

Name 2 oral viruses and their symptoms /complications

Answer 8

1.Herpes simplex type 1 virus - most common in mouth
gingivostomatitis - asymptomatic or ulcers
lays latent and secondary infection =cold sores
saliva transmitted

2.Epstein Barr virus ( ebv)- glandular fever
pharyngeal inflammation /tonsil large
saliva transmitted
children maybe subclinical

EBV CAN CAUSE BURKITTS lymphoma

Question 9

How can you prevent virus infections

Answer 9

PPE/appropriate hygiene ( IMPT in oral health)
Vaccination - complicated
Antiviral medications

Question 10

Name 2 antiviral medications and how they work

Answer 10

Amantadine ( influenza) - inhibits viral uncoating so genome not able be replicated

Acyclovir - inhibits DNA synthase - stops replication

Question 11

Why is forming an antiviral difficult

Answer 11

high mutation rates

Question 12

3 reasons Why a viral vaccination treatment is difficult

Answer 12

Antigenic shift
Antigenic drift
Low vaccination rates

All lead to increase in virus changes/mutations so vaccination then not effective )

Question 13

What is antigenic shift

Answer 13

2 or more strains virus combine - so sudden genome changes causing new subtypes and infect more virulently or other organisms

Question 14

What is antigenic drift

Answer 14

slow small mutations that accumulate overtime so eventually a new virus subtype emerges - vaccines then don’t work

Question 15

Why do antibiotics not kill viruses

Answer 15

No peptidoglycan cell walls, no ribosomes, not replicate their own DNA
Need host cells to replicate not replicate by themselves

Question 16

How are viruses replication different to bacterial cells

Answer 16

Need a host cell to replicate ( cannot replicate by themselves )
No binary fission