STD2 Flashcards
What are the features of HSV?
Double stranded DNA virus
Part of alpha-herpesviridae family
HSV1- oral vesicular lesions (may be responsible for genital lesions in young adults)
HSV2- genital vesicular lesions
What are the epidemiological features of HSV2?
400 million cases globally- 20 mil each year
Africa is most affected
What are the structural components of HSV2?
Glycoproteins- surface
Envelope- lipid membrane
DsDNA in core- >80 + genes
Tegument- mesh of viral proteins
Capsid
What are the steps in HSV2 cell cycle?
- Binding- GC bind to receptors on cell surface
- Entry- fusion of membranes, virus is internalised into cytoplasm
- Capsid transport- accumulates in nucleus
- Transcription
- Translation
- Replication of viral genome (rolling circle)
- Capsid assembly in nucleus of affected cell
- Glycosylation- glycoproteins are translated and glycosylated into ER
- Glycoprotein export- to cell surface
- Glycoprotein containing plasma membrane endocytosis
- GC within early endosomes fuse with caspids in cytoplasm
- Virus release into ECM
How long does it take for HSV2 to cause cell lysis?
24 hours- leads to vesicle and ulcer formation
How does HSV enter sensory nerve axons?
Via plexus of free nerve ending in epidermis
-> transpired into neuronal cell bodies in dorsal root ganglia
-> replicates and spreads to other neurone
What occurs in HSV2 latency?
Viral genome is maintained within ganglia for life of host as circular genetic elements called episomes in the nucleus
-> closely associated but not integrated into host DNA
What happens upon reactivation of HSV2 in ganglia?
Transport toward genital skin or mucosa
-> replication in epidermal cells after passage of virus across axonal epithelial gap
-> discrete shedding
How long does Herpes Genitalis primary infection take to present?
4-7 days usually
-> incubation period is 2-12 days
What are the signs and symptoms of HG primary infection?
Clusters of erythematous papules/vesicles
-> painful, burning
Fever
Headache
Malaise
Myalgia
What are the features of the prodrome in recurrent lesions of HG?
Itching
Tingling
Paraesthesia
What is different about recurrent infections of HG?
Fewer lesions
Unilateral
Generally no systemic symptoms
Resolves in 3-5 days
What are the stages in HG lesion development?
Vesicle pustule
Wet ulcer
Dry crusts
How long does primary infection of HG take to resolve in absence of antivirals?
3 weeks
How long do serum antibodies for HSV2 take to appear?
12 weeks
What is a non-primary infection of HG?
Infection with HSV1 or 2 in individual that has pre-existing antibodies to other HSV
-> milder presentation due to cross-immunity
How is Herpes Genitalis diagnosed?
History
Clinical presentation
Viral diagnostic assays- viral culture, PCR for HSV DNA
Serology- HSV antibodies
-> ELISA, IMMUNOBLOT, POCkit
What are some of the differential diagnoses for HG?
Infectious
- Chancroid
- Fungal infection
- Syphilis
- Secondary bacterial infection
Non-infectious
- Aphthous ulcers
- Behcets
- Neoplasm
- Psoriasis
- Sexual trauma
Why is screening for genital herpes not advised for people with no symptoms?
False postive results
Doesn’t prompt changes in sexual behaviour
Doesn’t stop the virus from spreading
What is the aim of anti-viral therapy in Herpes Genitalis treatment?
Reduce symptoms and likelihood of transmission (no cure)
What are the regimes for people with first episodes of HG?
Acyclovir- 400mg x 3 per day for 7-10 days
Acyclovir- 200mg x 5 per day for 7-10 days
Valacyclovir- 1g x 2 per day for 7-10 days
Famciclovir- 250mg x 3 per day for 7-10 days
What are some of the treatment options for recurrent HG?
Acyclovir- 400mg x 3 per day for 5 days OR 800mg x2 per day for 5 days
Famciclovir- 125mg x 2 per day for 5 days
What does effective episodic treatment require?
Initiation of therapy within 1 day of lesion onset or during prodrome
When is suppressive therapy considered for HG?
If patient has six outbreaks in a year
-> reduces frequency of recurrence by 70-80%
