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64 Cards in this Set

  • Front
  • Back
how big are viruses
20-450nm
what are the parts of a virus
nucleic acid
protein coat
envelope
what are some modes of human to human transmission
Skin
Saliva, nasal fluids
Urine
Faeces
Semen
Breastmilk
What viral infections are transmitted via skin contact
VZV/ smallpox
HSV1/2
What viral infections are transmitted via saliva
EBV, rabies, mumps, respiratory viruses
What viral infections are transmitted via urine
CMV
rubella
mumps
What viral infections are transmitted via feces
enteroviruses
- polio, rota, HAV
What viral infections are transmitted via semen
HIV, CMV, HBV
What viral infections are transmitted via breastmilk
CMV, mumps, rubella
What are the major sources of viral infection?
- human contact
- food preparation - fecal/oral
- insect/ animal bites
- infected water supply
What are common portals of entry for viruses? Give examples
conjunctiva
bites - arbovirus, rabies
scratch/injury - pox/papillomavirus
respiratory tract
alimentary tract
GU
anus
needles - CMV, HIV, HBV
What are common viral infections of the oral cavity?
rubella
coxackie
HSV
EBV
Measles
What are common viral infections of the conjunctiva?
Adenovirus conjunctivitis
HSV - dendritic ulcer
Herpes Zoster - ophthalmic
What are common viral infections of the GI?
Rotavirus
Enteric adenovirus
Norovirus
What are the routes of viral dissemination
Blood
lymph
nerves
which viruses are free in plasma
parvovirus
HBV
which viruses are red cell associated
Hemagglutination viruses
which viruses are lymphocyte associated
EBV, HIV
which viruses are monocyte/macrophage associated
HIV, CMV, HSV
How do viruses disseminate neuronally?
Enter nerve ending in muscle or dermis, travel axonally to synaptic junction then transneuronally
What is an example of a virus that is disseminated neuronally?
Rabies
What is tissue tropism
Preferential tissue for viruses, eg. hepatitis = liver, encephalitis viruses = brain,
What factors affect viral tropism?
- viral attachment to specific proteins
- specific receptors on cells
- permissiveness of cells to viral replication
- route of viral entry
- ability of virus to reach target tissues
What are consequences of viral infections?
Elimination
Persistence
a. chronic infection with viral shedding
b. latent infection
c. slow infection
i. degenerative
ii. neoplastic
What factors promote viral persistence?
Location - immunologically privileged sites - CNS
Tropism - lymphoid cells = inhibit immune response
Viral shedding - salivary or respiratory
What factors promote persistence of viruses
1. antigenic variation - HIV
2. silent infections - persistent but limited, HSV, VZV
3. Prevention of cell death - anti-apoptosis
4. Immune evasion - infection of lymphoid tissue limit response
How do viruses evade innate defences?
1. inhibit interferon
2. inhibit macrophages
3. inhibit activation of NK cells
How do viruses evade adaptive immune reponse
1. inhibit T cells
2. inhibit B cell activation
Which viral infections are considered to be chronic?
HBV, CMV, Rotavirus, Adenovirus
Which viral infections are considered to be latent?
EBV, HSV, HIV
Why does HBV persist?
1. young age of infection = 90% chronic
2. Inadequate T cell response
3. Non cytocidal, damage immune mediated
4. HBV pX gene - inhibits apoptosis
What is Cytomegalovirus?
DNA containing virus of Herpes group
70% seropositive, problem in immunocompromised
vertical transmission - cytomegalic inclusion disease
Where does CMV persist?
1. Salivary glands and kidneys - easy transmission to others
2. Monocytes - latent infection
What other immune effects of CMV
1. inhibit MHC expression
2. prevent NK cell killing
3. Dampen cytokine response
EBV
- herpesvirus
- infectious mononucleosis
- enters through pharyngeal epithelium
Where does EBV persist?
B cells
Pharyngeal epithelium
What malignancies are associated with EBV
Burkitt's lymphoma
nasopharyngeal carcinoma
What is Burkitt's lymphoma
common in africa, 5-12 yo
- requires malaria coinfection
- involves chromosomal translocations 8 to 2, 14, or 22
- b cell
Which viruses are associated with tumours?
HBV, HCV = hepatocellular carcinoma
Papillomaviruses = cervial and penile
HTLV 1 and 2 = Human T cell leukemia
HHV8 = Kaposi's sarcoma
How do viruses promote tumour production?
- stimulate cell division (oncogenes)
- inhibit apoptosis
- integration disrupts normal control mechanisms
What are types of glial cells?
Astroglia
Microglia
Oligodendrocytes
Schwann cells
What is a neuronal synapse
Where neurons and glia communicate - site of infection dissemination
How do microbes cross the BBB
1.Grow across - infect cells that compromise barrier
2.passively transferred across in intracellular vacuoles
3. Carried across by infected WBC
What is the result of a virus crossing BBB?
Encephalitis -
What is the result of a virus crossing the Blood CSF barrier?
Meningitis -
What is the choroid plexus?
capillaries and ependymal cells
What are ependymal cells
type of glial cell - simple epithelium - columnar/ cuboidal - that filter fluid out of capillaries and into ventricles of brain to produce CSF
apical surface - villi - mvmt csf and microvilli
what does csf do?
cushion to protect brain from physical mvmt
- homeostasis and metabolism of CNS
-- pH = ventilation rate and flow rate
-- lymphatic of cns
-- transport medium
what is the volume of CSF in adult?
-- in ventricles?
140mL
-- 25 mL
How much CSF is produced per day
600-700 mL
What determines the CSF pressure?
the rate of absorption of CSF by arachnoid villi
Where does CSF go once absorbed?
into the venous system through arachnoid granules
What is an arachnoid granule?
herniations of the arachnoid membrane through the dura into the lumen of the superior sagittal sinus
What happens to CSF composition in a viral infection?
Clear = aseptic meningitis
proteins slightly elevated
What is the normal protein and glucose amts in CSF?
Protein = 15-45 mg/dL
Glucose = 50-80 mg/dL
What is the normal pressure of CSF?
100-180 mm H2O, 8-15 mmHg with patient on side
200-300 with pt sitting up
What are S&S of CNS infection?
1. Altered awareness
2. headache
3. seizures
4. focal neuro signs
What is viral meningitis caused by?
Enterovirus - polio - fecal/oral,
mumps
HSV2
Which viruses cause true neuroptropism?
VZV and HSV
- 0.1-0.2% of cases get encephalitis
- virus travels retrograde to dorsal/ trigeminal ganglia to establish latent infection
Which are viral vectors for CSF infection?
Insect, rodents (hanta virus), larger mammals (rabies)
Which neurovirus is spread by arthropods?
Arboviruses - biological concept, not taxonomic
Number of arboviruses, 3 examples, how many in western hemisphere?
>500
bunyaviridae, togaviridae, flaviviridae
>30 arboviruses
Arboviruses pathogenesis
enter skin capillaries, viremia 2-4 days, to CNS to liver, Ab >1mo later
What are some syndromes of Arboviruses
encephalitis
liver disease
fevers
rashes
hemorrhagic rashes