Herpesviruses

Question 1

Discuss the general characteristics of herpes

Answer 1

> Primary infection can result in latent infection which results in the persistence of the viral genome within the host genome which no infectious virus is produced
Reactivation of the latent state can be asymptomatic viral shedding or clinical manifestations

Question 2

When does reactivation occur?

Answer 2

Reactivation occurs in immunocompromised patients

Question 3

Discuss the classification of the herpes virus according to the Baltimore classification and ICTV

Answer 3

Baltimore: dsDNA
ICTV: Icosahedral, enveloped ds linear

Question 4

How can the herpes virus be transmitted

Answer 4

• Direct contact with other body fluids

* incidence peak from 0 -5 years and late teens due to kissing and hugging

Question 5

What is the pathogenesis of herpes?

Answer 5

• Primary infection is usually subclinical
• the herpes virus initially replicates in the epithelial-producing characteristic lesions you can visually see.
• They then ascend into the sensory neuron to the dorsal root ganglia, where they remain latent
• Recurrence -associated with stress, infection.

Sometimes the HSV 1 is isolated from the trigeminal ganglion, autonomic ganglia, adrenal tissue, and brain whereas HSV 2 has been isolated from the sacral ganglia

HSV DNA passes along the axon ending where infection of epithelial cells can occur. Not all reactivation will result in visible lesions, therefore shedding of the reactivated HSV may be asymptomatics

Question 6

Discuss the clinical manifestations of herpes

5 marks

Answer 6

Cutaneous herpes 
ocular herpes 
herpes labialis 
Meningitis 
encephalitis 
Neonatal herpes (Mothers of neonates with herpes tend to have had a newly acquired genital infections

SEM infections
Disseminated herpes
CNS herpes

Question 7

How can HSV 1 and 2 be diagnosed?

4 marks

Answer 7

PCR and Serology ( ELISA; IgG and IgM )
Viral culture
Immunofluorescence staining

Question 8

How can herpes be treated

Answer 8

> Acyclovir ( inhibits viral DNA synthesis and it is thus effective against replicating viruses and cant be used to eradicate latent viruses & it depends on thymidine kinases for the addition of the first phosphorous, the rest is derived from the host cell )

• It is available in topical, oral, and IV ‘
• Can be used in pregnant women
• Oral should be used for mucocutaneous prophylaxis in immunocompromised patients
• IV should be used in severe infections

> For oral:
Famciclovir : 1500 mg onceper day
valaciclovir ( a prodrug for acyclovir ): 2g twice per day
acyclovir: 200 mg 5X days / 400 mg 3X day

> Topical :
Acyclovir apply for 5X for 4days
Docosanol cream: Apply 5x day until healed
Penciclovir: apply every 2 hours while awake for 4 days

> Prevent occurance
Acyclovir : 400 mg twicw a day
valacyclovir : 500 mg once a day
Sunscreen

> There are no vaccines for HSV