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