Herpes Virus Flashcards
How many herpes viruses are there?
8
Name the herpes viruses that affect humans?
Herpes simplex 1 Herpes simplex 2 varicella Zoster virus Cytomegalovirus Epstein Barr Virus Human herpes virus 6 Human herpes virus 7 Human herpes virus 8 (karposis sarcoma associated herpes virus)
How are herpes virus transmitted?
Saliva in asymptomatic and symptomatic individuals
Why are herpes virus often presented to you as a dentist?
Most can present as oral lesions
Describe herpes virus structure
Enveloped acquired from host cell
DS DNA
What are the 2 stages of herpes virus infection? describe each
Lytic infection and latent infection
Lytic - actively replicating new viruses produced causing host cell to burst and die
Latent = dormant in host cell - no active replication
Describe general life cycle of herpes simplex virus 1 and 2
- During primary infection the virus is exposed to epithelial cells where is attaches
- Capsid containing double stranded DNA is released into cytoplasm
- DS DNA moves in nucleus where new prodigy viruses are produced
- new viruses released from cell during lysis
- released in vesicles contains highly infectious fluid (also found in saliva)
- when the infection is under control from immune system some prodigy viruses will travel up sensory neurones to the spinal ganglia where they sit dormant until reactivated and they travel back to epithelial cells
Describe primary infection?
First infection with either HSV1 or 2 causing active viral replication in mucosal tissues.
Normally symptomatic but can be asymptomatic
Describe latency?
Virus sits in nerve cell bodies in spinal cord with no viral replication
Describe reactivation?
Latent virus reactivates and active viral replication in mucosal tissues resumes
At what age do most primary infections occur in UK?
Before 5
What is the seroprevalence of HSV1 and HSV2 in UK?
1 = 50-70% 2 = 10%
How is HSV spread?
Oral - close contact e.g. kissing
Genitals - sexual contact
From mother to baby
Describe oral manifestion of primary HSV infection?
a) what virus
b) symptoms - sytemically
c) symptoms - orally
d) complications
a) Most commonly HSV1 but can be HSv2
b) usually asymptomatic
c) severe gingivostomatitis
d) may require hospitalisation due to dehydration or pain
Oral reactivation of HSV1?
Cold sores - rarely intra-oral
Oral reactivation of HSV2?
Generally doesn’t reactivate
Oral reactivation of HSV
a) cause
b) triggers
c) sensation
d) duration
a) unknown
b) stress, fever, menstruation, cold, UV
c) tingling or itching
d) 5-12 days
HSV genital disease
a) primary infection
b) reactivation agent
c) primary vs reactivation severity
a) HSV1 or HSV2
b) HSV2 only
c) primary is more severe, reactivation is usually asymptomatic
Why can HSV genital disease be spread unknowingly?
Reactivation is often asymptomatic
Main complications of HSV?
Secondary bacterial infection - rash destroys epithelia so bacteria can penetrate
Corneal ulcers - loss of vision, risk of scarring
Meningitis - self limiting, HSV2, can be recurrent (mollarets meningitis)
Herpes simplex encephalitis, life-threatening, usually HSV1
Neonatal hepres simplex - life threatening
Life threatening infection in immunocompromised
What is herpetic whitlow?
Lesions on thumb or fingers due to herpes simplex virus
What type of people are susceptible to herpetic whitlow?
Thumb suckers - infected saliva penetrates skin
Occupational health hazard when correct PPE not used
How can HSV affect the eye?
Occular infection - corneal ulcers - need to be treated promptly or scarring and loss of vision
What causes neonatal infection?
Directly through birthing process - if mother infected with HSV, could be secreted in vaginal fluid and infect the baby
Or infected family ember kissing baby shortly after birth
How can neonatal infection present?
Oral, eye, skin lesions
CNS and disseminated organ involvement
What is the most common cause of viral encephalitis?
HSV encephalitis
How does HSV encephalitis present?
Fever, headaches, odd behaviour
Why can HSV encephalitis be more problematic in older patients?
Symptoms (fever, heachahe, odd behaviour) can be misdiagnosed - leads to late diagnosis = high mortality rate
How is HSV diagnosed?
PCR - polymerase chain reaction (lesion or cerebrospinal fluid swab)
Treatment for HSV?
Acicilovir and valaciclovir - inhibit viral polymerase
How are HSV treatments selective for infected cells?
Needs to be activated by viral enzyme (thymidine kinase)
Why is valaciclovir better thank aciclovir?
Better oral bioavailability - less dosage but more expensive
How does varicella zoster virus present?
Chicken pox
How is varicella zoster virus transmitted?
Oral or respiratory route, can be aerosolised
Where does replication of varicella zoster virus occur and what does this cause?
Lymph nodes
Primary viraemia - virus enters the blood stream and travels to liver and spleen
When VZV reaches liver and spleen what occurs?
Replication of virus and secondary viraemia - causing spread of virus to skin
Can VZV become latent?
Where?
Reactivation?
Yes
In dorsal route ganglion
Reactivation as shingles (zoster)
Describe primary chickenpox infection?
a) causative virus
b) symptoms before rash
c) where is the rash found?
d) development of vesicles
e) oral manifestation
a) VZV
b) fever
c) centripetal - head, neck trunk
d) macules, papules, vesicles, pustules
e) oral vesicles - extremely painful
Seroprevalance of VZV in UK?
90%
When is VZV infectious?
2 days before rash until full crusting of vesicles
How can shingles present?
Dermatomal - one area
opthalmic
oral
Diagnosis of VZV?
Clinical or PCR
When is treatment for chicken pox required?
Increased risk - pregnant women, immunocompromised, severe disease involving lungs
How can chicken pox be treated?
Zoster immunoglobulin - bag of antibodies
When is zoster immunoglobulin used?
Early pregnancy when exposed and not immune
Why can varicella vaccine not be given to pregnant ladies or immunocompromised?
Live attenuated vaccine
Indications for varicella vaccine in UK?
Healthcare workers, immunocompromised child
Shingles vaccine - when is it given, why?
aim to boost immunity and prevent reactivation
given to over 70 year olds who have been exposed to chicken pox
Transmission of cytomegalovirus (CMV)?
Direct contact with infected secretions (saliva, genital)
Primary infection CMV?
Usually asymptomatic, occasionally cause glandular fever like picture
CMV concerns?
Congenital infection
Severe disease in immunocompromised
Epstein Barr virus presentation?
Young children - asymptomatic or sore throat
Adolescents - glandular fever
Often associated with lymphomas or cancer
Where does EBV become latent?
B lymphocytes
EBV transmission?
Saliva or sexual contact
How can EBV reactivate?
Oral hairy leukoplakia
What does oral hairy leukoplakia suggest of the patient?
Sign of immunosuppression or HIV infection
How does Human Herpes virus 6 and 7 present?
48 hour non specific rash in infants (roseola infantum)
How does HHV 8 present? What is it related to?
Kaposi’s sarcoma associated virus
Associated with HIV
