Viral Infections Flashcards
What is the 3 main structures of a virus?
- DNA
- RNA (double/single)
- mRNA
- Nucleic acid protected by capsule
Mechanism of a virus?
- lands on host cell membrane and capsule integrates with it
- releases nucleic acids into cell
- if RNA, can be translated into proteins which produce even more viruses
For other viruses, RNA and DNA can be translated into more nucleic acids (transcription) which get translated into proteins.
Transcripted nucleic acids come together come together with new translated proteins to form more viruses and get exported out of the cell.
How do viruses that need DNA to replicate work?
- DNA is integrated into host DNA and use host cellular ribosomes and mechanisms to produce more viruses
- can only replicate inside host (ie live cells, not Petri dishes).
Issue with viruses that need host DNA to replicate?
Can only replicate inside host ie live cell so cannot grow on a Petri dish which means can’t do microbiology tests on it well - issue with diagnosis etc
How do antivirals work?
- virus penetration
-uncoating - nucleic acid synthesis and integration
- virions production
- immune modulators = response to kill cells with virus to stop replicating
Most common anti viral example and mechanism ?
Acyclovir used for herpes labialis
Mechanism = inhibits viral DNA polymerase so prevents DNA replication
What is herpes virus?
Group of DNA viruses
Three main groups:
1. HSV1 = oral lesions
2. HSV2 = genital lesions
3. Varicellar Zoster = chickenpox / shingles
What is the structure of herpes virus ?
In the middle there is the DNA with a DNA capsule
Complex membrane enhances host cell attachment
Why do viruses affect different parts of the body?
They have different tropisms eg HSV1 is oral mucosa, HSV2 is genital etc
How does HSV1 present in children?
Primary herpetic gingivostomatitis
Presents with fever, illness, multiple red mouth ulcers
How does Varicella Zoster virus present?
Chickenpox in children
Presents with mild illness, itchy rash, settles down over a week or two.
What is the main issue with post viral diseases?
Following initial infection=
- infection occurs and pt has symptoms and then clear up eventually
- Viruses have tropisms towards neurones and travel up to the neurone nucleus, sits there and remains dormant.
- HVS1 is in trigeminal ganglion , HSV2 is the nerves around the genital skin
- Virus can reactivate, replicate and travel back down neurone to the mucosa they initially infected
- results in local infection in area end of neurone ( HSV1 herpes labialis, HSV2 genital herpes)
What is another term for a cold sore?
Herpes labialis
How is herpes labialis reactivated?
Stress
UV
Immune suppression
How does herpes labialis present orally?
tingling for a few days which then turns into an ulcer that then ulcerates and crusts
resolves in a couple days
How does genital herpes present?
tingling for a few days which then turns into an ulcer that then ulcerates and crusts (same as herpes labialis but in genital areas)
Why cant we treat pts with cold sores?
During the infective stage, the blisters are highly contagious and if they burst, they release lots of viral particles.
If this splashes in eyes = ocular herpes (sight threatening)
On finger= painful ulcer on finger
What does varicella zoster virus present as initially, where does it lie dormant and what does it reactivate as?
- Chicken pox
- Lies dormant in trigeminal ganglion (opthalmic/max/mand branch, any of them)
- Shingles
Is VZ infection more or less serious than herpes and why?
More serious
presents as lots of ulcers (usually unilaterally) and really painful.
Can cause post herpetic neuralgia (complication of shingles) - intense intermittent pain along nerve of head and neck.
What is Epstein Barr virus a type of?
Herpes virus
How does Epstein Barr virus manifest as a disease?
Produces infectious mononucleosis disease (“mono” aka kissing disease aka glandular fever)
- exremely infectious and common in teens
What is the mechanism of the Epstein Barr virus?
Lives in pharynx, replicates here and then the pharyngeal tonsils secretes viral particles
How does Epstein Barr virus infection present?
Sore throat
Malaise
LN tender
Tonsil inflammation (white reticular patches on tonsils)
Lasts 3-5 days but can get post viral tiredness/malaise for several months after
What type of virus causes hairy leukoplakia and how does it present ?
- EBV
- White patches
