Human Herpes Virus Flashcards
What is the size of the Herpes Virus?
120-200nm
What disease does Herpes simplex virus 1 & 2 cause?
Oropharyngeal & Genital Herpes
(HSV 1 - mainly oral infections
HSV 2 - mainly genital infections)
What disease does Varicella-Zoster Virus (HHV-3) cause?
Chicken pox (Varicella) / Shingles (Zoster)
How does HSV-1 cause oral infections?
Herpetic gingivostomatitis
- The virus enters trigeminal sensory neurones
- Migrates to trigeminal ganglion
- In 50% of cases it remains dormant in the trigeminal ganglion
- In 50% of cases it becomes reactivated and migrates to peripheral nerve endings were active viral particles are shed.
How is the HSV reactivated?
Reactivation of Herpes Simples Infection (Herpes Labialis - cold sores)
- UV light
- Stress
- Illness
- Immuno-suppression
The lesion resolves. The virus lays dormant again in trigeminal ganglion until reactivated
Which group of people does herpetic gingivostomatitis (HSV-1) mostly affect?
Mainly affects young children (usually mild, may go unnoticed)
Sometimes young adults (often more severe)
What are the clinical features of Herpetic Gingivostomatitis (HSV-1)
- Incubation period 3-10 days
- Duration 5-14 days
- Multiple Vesicles - rupture to form extensive sloughing ulcers
- Gingivitis with erythema and sloughing
- Malaise, pyrexia, lymphadenopathy
How are we able to investigate Herpetic Gingivostomatitis (HSV-1)
- Rising antibody titre
- Presence of IgM antibodies
- Viral culture (now mainly PCR)
What is the Basic method of PCR
- ) DENATURE DNA to single stands
- ) ANNEALING PRIMERS of specific primers to DNA
- ) EXTENSION BY POLYMERASE
- ) AMPLIFICATION - Repeat 30-35 times
How do we manage Herpetic Gingivostomatitis (HSV-1)
- Acyclovir (200mg 5 x daily for 5 days) if found early or in immunocompromised
- Fluids and soft diet
- Analgesics/Antipyretics
- Local antiseptics e.g. chlorhexidine
- Topical analgesics e.g. Difflam
Action of Acyclovir
- HSV thymidine kinase phosphorylates guanosine (G) when HSV DNA replicates
- Human cells cannot phosphorylate ACV very well
- In HSV-infected cells, ACV is phosphorylated by the viral TK enzyme to ACV-P
- ACV-P then inhibits virus replication
What are the clinical features Herpes Labialis (Reinfection 2 HSV) - Cold Sores
- Prodromal irritation
- Vesicles at or near mucocutaneous junction of lips
- Crusting lesions lasting 7-10 days
- usually reoccur at same sites
- Rarely:
may occur, intra-orally, in nose or elsewhere on skin
Management of Herpes Labialis
- Acyclovir cream 5% if used very early
- OTC drying and antibacterial agents
PROPHYLACTIC TMT:
]• Rarely justified
• Prophylactic acyclovir will prevent lesions in the immunocompromised or those susceptible to erythema multiforme
Value of Acyclovir in Herpes Labialis
- Reduces duration of pain by 1.4 days
- Reduces occurrence of new lesions by at least 50%
Reduces time to lesion crusting by 2.1 days
What are the features Herpetic Whitlow
• Herpetic infection of the fingers from handling the oral tissues of someone with active 1 or 2 HS lesions
- Very painful
- Very difficult to treat
- Prevention better than cure (wear gloves)
What is HSV Encephalitis
- Mainly affects frontal lobes of the brain
- 70-80% mortality if untreated
- Only 3% of survivors return to normal
Usually only people >50 years (HSV-1) and neonates (HSV-2) affected
Feature of HSV Encephalitis
ADULTS (HSV-1)
• Headache and behavioural changes over several days
• Fever
• Only 11% of cases have a history of recurrent HSV infections
NEONATES (HSV-2)
• Skin rash, lesions and CNS symptoms
- Virus present in liver, lung and adrenal glands
- Respiratory distress
- Fits and convulsions
- Raised cranial pressure
- 1 in 300,000 births in UK
What is HHV-3
HHV-3 = Varicella-Zoster Virus
- Primary Infection - Chicken pox (Varicella)
- Secondary Infection - Herpes zoster (Shingles) - Chest and Back most common
(secondary infection being reactivated by Age, Stress, Illness, Immunosuppression)
What are the Three phases of infection with Herpes Zoster (2nd infection)
- ) Pre-herpetic neuralgia
- ) Rash
- ) Post-herpetic neuralgia
What are the clinical features of Pre-herpetic neuralgia:
- Pain in the distribution of the affected division of the trigeminal nerve
- Prior to the development of the rash
- May mimic dental pain
Clinical features of the rash in Herpes Zoster infection
- Unilateral vesicles in the distribution of a branch of the trigeminal nerve
- These vesicles break down to form:
- Ulcers (mucosa)
- Crusting lesions (skin)
- Lasts 2-3 weeks
- In the eye:
- Glaucoma
- Cataract
- Double vision
- Scarring of the cornea
How do we manage Herpes Zoster Infection?
- Acyclovir 800mg 5 x daily for 7 days if seen soon after lesions develop
- Analgesics
- Ophthalmic referral if eye involved
- Avoid contact with children
New alternatives to acyclovir:
- Valaciclovir 1g 3 x daily for 7 days
- Famciclovir 250mg 3 x daily for 7 days
Describe Post-herpetic neuralgia
- 10% of patients go on to get extremely unpleasant intractable burning pain in the distribution of the affected nerve.
- More common in the elderly
- Effective early treatment of zoster may decrease risk of neuralgia
- Treat pain with tricyclic anti-depressants and neuropathic pain drugs
What are the associated diseases with HHV-4 - Epstein-Barr Virus (EBV)
- Infectious Mononucleosis (Glandular fever) - Acute Primary infection with EBV
- Burkitt’s Lymphoma - a B-cell malignancy
- Nasopharyngeal Carcinoma - an epithelial cell malignancy
- Oral Hairy Leukoplakia - seen in AIDS patients and some transplant recipients.
