Herpes infections Flashcards
Fun fact: where does the word herpes come from?
The Greek word herpein (“to creep”), referring to the latent, recurring infections typical of this group of viruses.
In total, how many herpes viruses can affect humans?
8 - confusingly named as both strains of human herpes virus (HHV) and their own name: -
More common HHV1 - HSV1 HHV2 - HSV2 HHV3 - VZV HHV4 - EBV HHV5 - CMV Less common HHV6 - Roseolovirus HHV7 - ? sad no name virus :( HHV8 - Kaposi's sarcoma-associated herpesvirus (KSHV)
Name the 5 most common species of herpes virus
Herpes simplex virus 1 (HSV1) Herpes simplex virus 2 (HSV2) Varicella zoster virus (VZV) Epstein-Barr virus (EBV) Cytomegalovirus (CMV)
(HHV1-5)
Which 3 herpes viruses are neurotropic and what does this mean
HSV1, HSV2 and VZV
- Capable of infecting nerve cells, which are also the site of latency for these 3 viruses
What sort of genetic material do the neurotropic herpes viruses possess?
dsDNA
Does HSV have an animal reservoir?
No
How is HSV transmitted?
Muco-cutaneous contact
How is VZV transmitted?
Droplet spread
Which cell types undergo lytic infection by HSV?
Fibroblasts and epithelial cells
In which part of the nervous system does HSV have a persistent latent phase?
The dorsal root ganglion
Where in the human body does VZV replicate?
Initially lymph nodes followed by liver and spleen
Describe the rash caused by VZV. How long after infection does this rash arise?
Vesicular
~48 hours post
What is the incubation period for oral HSV (cold sore/Herpes labialis)?
2-12 days
Describe a coldsore infection
Severe painful ulceration on/around the lips Tendency to coalesce Erythematous base Fever Submandibular lymphadenopathy
What is the main differential diagnosis for herpes labialis?
Herpangina (caused by Coxsackie A virus)
What is the incubation period for genital herpes?
4-7 days
Describe the presenting symptoms of genital herpes
Fever Dysuria Malaise Inguinal lymphadenopathy Pain++ Vesicular rash
What percentage of primary genital herpes cases are followed by herpes meningitis?
4-8%
Occurs 1-2 weeks after primary infection
What is sacral radiculomyelitis/radiculitis?
A self-limiting syndrome of acute urinary retention triggered by HSV2
AKA Elsberg syndrome
Occurs in ~5% genital herpes
Which type of HSV causes cold sores?
HSV1
Which type of HSV predominantly affects the genitals?
HSV2
Remember: 2 people have sex
Name the disease caused by an ocular HSV 1 infection
Herpetic keratitis
NB can also be caused by HSV2, but much less common
Describe the presenting features of herpetic keratitis
Unilateral/bilateral conjunctivitis
Pre-auricular lymph node involvement
Without treatment, what might herpetic keratitis progress to in healthy patients?
Acute retinal necrosis
What might herpetic keratitis progress to in immunosuppressed patients?
Progressive Outer Retinal Necrosis (PORN)
Other than HSV, which other herpes viruses can cause Progressive Outer Retinal Necrosis (PORN)?
VZV, EBV, CMV
At what stage of pregnancy is a mother at risk of transmitting HSV to fetus?
3rd trimester
Primary infection in 1st and 2nd trimesters not associated with increased risk to fetus
What is the treatment for maternal primary HSV infection during 3rd trimester?
Oral/IV acyclovir 6 weeks before EDD
If genital infection persists/presents close to EDD C-section is indicated
When is HSV most commonly transmitted from mother to child?
Most often at delivery
Postnatally via mother with cold sores kissing baby
Rarely transmitted in utero
How can neonatal HSV present?
- Fetal loss
- Skin, eye and mouth (SEM) lesions at 7-12 days post-partum. Long term ocular and neural sequelae
- Disseminated disease +/- vesicles at 4-11 days post-partum. Risk of fuminant hepatitis or multi-organ failure. 80% mortality
- Neurological disease +/- SEM at 17-18 days post-partum. 50% mortality
(In summary: it’s really bad news)
Which form of HSV most commonly causes encephalitis?
HSV1 in 90% cases
remember: we have 1 brain
Describe the presenting features of herpetic encephalitis?
Flu like prodrome for 2 weeks Focal neurology Fever Confusion Behavioural change Decreased consciousness Seizures Nausea and vomiting Coma Death
Which age group is most likely to be affected by herpetic encephalitis?
> 60s (half of all cases are in this age group)
What is Mollaret’s meningitis?
Benign recurrent aseptic meningitis usually caused by latent HSV2
Which lobes of the brain are affected by herpetic encephalitis?
Fronto-temporal and parietal (lesions seen on CT/MRI)
What CSF results would be expected in herpetic encephalitis?
Lymphocytic pleiocytosis
Cytology may be normal
Normal glucose
Raised protein
How is herpetic encephalitis diagnosed?
Definitive diagnosis can only be made by PCR of CSF or brain biopsy.
PCR slow, treatment should be started on clinical suspiscion.
False negatives possible with PCR - should not exclude if negative
What is the treatment for herpetic encephalitis?
IV acyclovir stat
10mg/kg TDS then oral acyclovir for total of 2-3 weeks
List 6 skin infections caused by herpes viruses
Herpes gladitorum/scrum pox Herpetic whitlow Erythema multiforme HS dermatitis Eczema herpeticum Zosteriform HS (painless)