Virology Flashcards by Michael Nel

Defn aseptic meningitis

Clinical/lab evidence of meningitis with neg bacterial culture

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Viral injury to CNS occurs by either

Cytolitic replication

Immunopathology

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Common causes of aseptic meningitis

Enteroviruses
Mumps

(RARE -HSV2)

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Histology of post infectious encephalomyelitis (ADEM)

Lymphocytic infiltrate

Peri vascular cuffing of adjacent blood vessels

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Lesions seen in ADEM

White matter lesions

NB molecular mimicry to myelin (T cell destroys)

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Cause of post infectious encephalomyelitis

Almost all viruses

Post vaccine

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Lesions seen in encephalitis

Grey matter lesions

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Signs in encephalitis

Fever
Drowsy
Decreased consciousness 
Focal signs
Confusion 
Convulsions

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Common causes of encephalitis

Herpes simplex
Rabies
Arboviridae

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Pathogenesis of acute flaccid paralysis

Enter via gut. Bloodstream. Cell bodies of motor neurons = grey matter lesions

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Spread of measles

Reap droplets

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Vaccine for measles

Live attenuated vaccine

Not earlier than 9 months = mother IgG prevents vaccine replication

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Who doesn’t get measles vaccine

Pregnant
Severely immunocomprimsed
(<1 year)

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Possible syndromes from measles in CNS

Acute Measles Post infectious encephalitis
Measles inclusion bodies (immunocomprimsed)
SSPE

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Spread of mumps

Resp droplets

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Distinguishing feature of mumps

Parotitis

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Period of aseptic meningitis in relation to parotitis in mumps

One week before to three weeks after

What may follow aseptic meningitis in mumps

Encephalitis

Vaccine for mumps

Live attenuated

Not in SA

What is seen in 25% post pubertal men in mumps

Orchitis (may lead to infertility)

How to diagnose mumps

Serology
Culture saliva/urine
PCR

Is it useful to do PCR in post infectious encephalomyelitis

No. Immune reaction so no virus in CSF

Spread of enteroviruses

Fecal oral

What do enteroviruses most commonly cause in CNS

Aseptic meningitis

Acute flaccid paralysis

Three clinical outcomes of polio

Asymptomatic Minor febrile illness Major illness - Acute flaccid paralysis - aseptic meningitis - respiratory paralysis

Diagnosis of polio

PCR | Culture

Vaccine for polio

``` Live attenuated oral (IgA) Formalin Inactivated (IgG) ```

Why six doses of polio virus vaccine

Only one strain 'takes' each time

Four ways viruses can enter CNS

Anterograde neuronal transport Retrograde neuronal transport (rabies, HSV) Trojan horse by lymphocyte/ macs cell lines (west Nile, HIV) Infection of endothelium in blood vessels in BBB

Post exposure prophylaxis for rabies

Rabies Ab | Rabies vaccine

Lethal syndrome that may develop after influenza

Reye's syndrome <18 Aspirin ingestion

Pathogenesis of post infectious encephalomyelitis

Following viral infection, T cell confuse myelin in CNS with viral antigen epitope = molecular mimicry. White cell lesions in CNS

How does the immune system cause damage in viral infections?

- cytotoxic T cells attack virus infected cells - antibody binding to infected cell attracts NK cells and triggers complement mediated cell lysis - antigen-antibody complexes cause inflammatory reactions

Pathogenesis of post-infectious encephalomyelitis

T cells confuse the myelin in the brain with viral antigen epitope

3 most common causes of uncomplicated viral meningitis

- mumps - HSV - enteroviruses

2 polio vaccines

OPV - live attenuated - at birth | IPV - killed - 6/10/14/18 weeks

Post- exposure prophylaxis after dog bite

- tetanus toxoid - wash with soap - antibodies into wound/deltoid - vaccine days 0,3,7,14 - again on day 28 if immunocomp

High risk HPV types

- 16,18,31,33,35

Virus causing progressive multifocal leukoenceohalopathy

JC virus

Who is at risk of PML.

Immunocomp patients

3 forms of measles in the CNS

- acute measles post-infectious encephalitis (immunocompetent, AI,days to weeks, varied outcome) - measles inclusion body encephalitis (immunocomp, weeks to months, virus present, fatal) - subacute sclerosing panencephalitis (immunocompetent, years, slow progression to death)

Difference between PIEM and GBS

GBS is demyelination of the peripheral nerves | PIEM is due to demyelination if the CNS