Herpes Flashcards
What are the 8 human herpesvirus types?
- HHV1 - Herpes simplex virus type 1 (HSV1)
- HHV2 - Herpes simplex virus type 2 (HSV2)
- HHV3 - Varicella-zoster virus (VZV)
- HHV4 - Epstein-Barr virus (EBV)
- HHV5 - Cytomegalovirus (CMV)
- HHV 6 - Human herpesvirus type 6
- HHV 7 - Human herpesvirus type 7
- HHV 8 - Human herpesvirus type 8
Describe the structure
Envelope, genome etc
- 100-180nm diameter
- Regular icosahedral capsid composed of 162 capsomeres
- Ether-sensitive outer membrane
- Double-stranded DNA
Describe the replication
- Viral envelope binds to cell receptors and fuses with cell membrane. Virus uncoats.
- Viral DNA replicates and is transcribed within nucleus, giving rise to structural proteins.
- Viral DNA is packaged into capsids.
- Viral glycoproteins are incorporated into nuclear membrane to form viral envelope and virions bud out through nucleus and released at cell surface.
What does it grow in?
Tissue culture
What does it produce?
- Pocks on chorio-allantoic membrane
- Characteristic giant cells and eosinophilic intranuclear inclusion bodies (except EBV)
Describe the latency
- Following primary infection, herpesvirus sequester into sites where they remain quiescent
- Viral reactivation leading to recurrent infection may be triggered by factors such as immunosuppression
Primary site of HSV1
Lips
Transmitted by kissing
Primary site of HSV2
Genitalia
Transmitted sexually and perinatally
Describe the pathology of HSV1 and HSV2
- Vesicular eruption
- proliferation
- ballooning degeneration
- acidophilic intranuclear inclusions - Encephalitis
- meningitis
- perivascular infiltration
- neuronal degeneration - Early inclusion
- cowdry type A inclusion body
Describe the primary infection of HSV1 and HSV2
Mostly subclinical
May be severe with rash lasting 3-4 weeks in some adults
Where does HSV1 and HSV2 travel and how does it reactivate?
- Travels along sensory nerves to sensory ganglia where it persists lifelong in a latent state
- Reactivation by factors involving virus travelling down nerve fibres resulting in lesions
What are the factors affecting reactivation of HSV1 and HSV2?
- Immunosuppression
- Fever
- Stress
- Menstruation
What are the clinical presentation of HSV1? (8)
- Acute herpetic gingivostomatitis
- Herpes labialis
- Herpetic whitlow
- Eczema herpeticum
- Kereatoconjunctivitis
- Aseptic meningitis
- Acute necrotising encephalitis
- Disseminated herpes in immunocompromised subjects
What does HSV1 acute herpetic gingivostomatitis cause? How common is it? How does it spread?
- Vesicles on buccal mucosa, gums ulcerate with grey slough
- Fever
- Lymphadenopathy
- Commonest primary disease esp. in young children
- Spread mainly by kissing
What does HSV1 herpes labialis cause? How does it come about?
- Cold sore
- Herpes febrilis
- Crop of vesicles at mucocutaneous junction of lips or near nose (later with painful ulcers)
- Commonest recurrent disease from reactivation of HSV in trigeminal ganglion
What does HSV1 herpetic whitlow cause? How does it come about?
- Implantation of HSV into fingers resulting in lesions with serous exudate
- Hands of doctors, dentists and nurses in contact with oral secretions of infected patients
What does HSV1 eczema herpeticum cause?
- Kaposi’s varicelliform eruption
- Superinfection of chronic eczematous skin with extensive vesiculation, fever and significant mortality
What does HSV1 keratoconjunctivitis cause?
- Edema and vesicle of eyelids
- Cornea - dendritic keratitis, ulcers, opacification, blindness
What does HSV1 acute necrotising encephalitis cause? How to diagnose?
- Sudden fever, confusion, headache
- Temporal lobe necrosis
- High morbidity with neurological deficits, high mortality
- CSF - lymphocytosis
- PCR for HSV
- Brain biopsy - viral isolation
What are the clinical presentations of HSV2? (3)
- Herpes progenitalis
- Neonatal herpes
- Cervical and vulvar carcinoma
What does HSV2 herpes progenitalis result in? How does it come about?
- Sexually transmitted vesiculoulcerative lesions of genitalia (penis, perineum, vulva, vagina, cervix)
- Fever
- Malaise
- Lymphadenopathy
- Recurrent lesions from reactivation of latent HSV2 in lumbar and sacral ganglia
What does HSV2 neonatal herpes result in? How does it come about? How to prevent?
- Jaundice, hepatosplenomegaly, thrombocytopenia, large cutaneous vesicles
- Severe generalised infection acquired from infected birth canal of mother (esp. without protective maternal antibodies)
- Caesarian delivery for pregnant women with severe genital herpes
Spectrum from subclinical to severe
How to diagnose HSV1 and HSV2?
- Virus isolation
- Vesicle fluid, skin swab, saliva, tears, corneal scrapings (multinucleated giant cells with Tzanck cell microscopy), brain biopsy
- Inoculation of cell cultures (CPE of rounded cells in 48-72 hours) - Serology
- Primary HSV infection: neutralising HSV IgM antibodies
- Significant rise in antibody titre 2-4 weeks after primary infection
- Recurrent infectino: High levels of existing antibodies and no rise in titre
How to treat HSV1 and HSV2?
- Acyclovir IV, PO or topical
- Valaciclovir
