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USMLE Step I Microbiology > RNA viruses > Flashcards

RNA viruses Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

Reoviruses–envelope?

A

NO

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2
Q

Reoviruses–RNA structure

A
  • DS linear
    • 10-12 segments
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3
Q

Reoviruses–capsid symmetry

A
  • icosahedral
    • double
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4
Q

reoviruses–medical importance

A
  • coltivirus–Colorado tick fever
  • Rotavirus–#1 cause of fatal diarrhea in children
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5
Q

Picornaviruses–envelope

A

NO

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6
Q

Picornaviruses–RNA structure

A
  • SS + linear
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7
Q

Picornaviruses–capsid symmetry

A
  • icosahedral
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8
Q

Picornaviruses–medical importance

A
  • Poliovirus–polio Salk/Sabin vaccines–IPV/OPV
  • Echovirus–aseptic meningitis
  • Rhinovirus–“common cold”
  • Coxsackievirus
    • aseptic meningitis
    • herpangina–mouth blisters, fever
    • hand, foot, and mouth disease
  • HAV
    • “PERCH”
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9
Q

Hepevirus–envelope

A

NO

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10
Q

Hepevirus–RNA structure

A
  • SS + linear
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11
Q

Hepevirus–capsid symmetry

A
  • icosahedral
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12
Q

Hepevirus–medical importance

A
  • HEV
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13
Q

Caliciviruses–envelope

A

NO

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14
Q

Caliciviruses–RNA structure

A
  • SS + linear
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15
Q

Caliciviruses–capsid symmetry

A
  • icosahedral
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16
Q

Caliciviruses–medical importance

A
  • norovirus–viral gastroenteritis
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17
Q

Flaviviruses–envelope

A

YES

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18
Q

Flaviviruses–RNA structure

A
  • SS + linear
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19
Q

Flaviviruses–capsid symmetry

A
  • icosahedral
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20
Q

Flaviviruses–medical importance

A
  • HCV
  • Yellow fever
    • arbovirus, arthropod borne (mosquitoes, ticks)
  • Dengue
    • arbovirus, arthropod borne (mosquitoes, ticks)
  • St. Louis encephalitis
    • arbovirus, arthropod borne (mosquitoes, ticks)
  • West Nile virus
    • arbovirus, arthropod borne (mosquitoes, ticks)
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21
Q

Togaviruses–envelope

A

YES

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22
Q

Togaviruses–RNA structure

A
  • SS + linear
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23
Q

Togaviruses–capsid symmetry

A
  • Icosahedral
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24
Q

Togaviruses–medical importance

A
  • Rubella
  • Eastern equine encephalitis
    • arbovirus, arthropod borne (mosquitoes, ticks)
  • Western equine encephalitis
    • arbovirus, arthropod borne (mosquitoes, ticks)
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25
Q

Retroviruses–envelope

A

YES

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26
Q

Retroviruses–RNA structure

A
  • SS + linear
    • 2 copies
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27
Q

Retroviruses–capsid symmetry

A
  • icosahedral
    • HTLV
  • complex and conical
    • HIV
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28
Q

Retroviruses–medical importance

A
  • have reverse transcriptase
  • HTLV–T cell leukemia
  • HIV–AIDS
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29
Q

Coronaviruses–envelope

A

YES

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30
Q

Coronaviruses–RNA structure

A
  • SS + linear
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31
Q

Coronaviruses–capsid symmetry

A
  • helical
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32
Q

coronaviruses–medical importance

A
  • “common cold”
  • SARS
  • MERS
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33
Q

Orthomyxoviruses–envelope

A

YES

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34
Q

Orthomyxoviruses–RNA structure

A
  • SS - linear
    • 8 segments
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35
Q

Orthomyxoviruses–capsid symmetry

A
  • helical
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36
Q

Orthomyxoviruses–medical importance

A
  • influenza virus
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37
Q

Paramyxoviruses–envelope

A

YES

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38
Q

Paramyxoviruses–RNA structure

A
  • SS - linear
    • nonsegmented
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39
Q

Paramyxoviruses–capsid symmetry

A
  • helical
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40
Q

Paramyxoviruses–medical importance

A
  • PaRaMyxovirus:
    • Parainfluenza–croup
    • RSV–bronchiolitis in babies
      • Rx–Ribovirin
    • Measles, Mumps
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41
Q

Rhabdoviruses–envelope

A

YES

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42
Q

Rhabdoviruses–RNA structure

A
  • SS - linear
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43
Q

Rhabdoviruses–capsid symmetry

A
  • helical
44
Q

Rhabdoviruses–medical importance

A
  • Rabies
45
Q

Filoviruses–envelope

A

YES

46
Q

Filoviruses–RNA structure

A
  • SS - linear
47
Q

Filoviruses–capsid symmetry

A
  • helical
48
Q

Filoviruses–medical importance

A
  • Ebola/Marburg hemorrhagic fever–often fatal!!
49
Q

Arenaviruses–envelope

A

YES

50
Q

Arenaviruses–RNA structure

A
  • SS + or - circular
    • 2 segments
51
Q

Arenaviruses–capsid symmetry

A
  • helical
52
Q

Arenaviruses-medical importance

A
  • LCMV–lymphocytic choriomeningitis virus
  • Lassa fever encephalitis–spread by rodents
53
Q

Bunyaviruses–envelope

A

YES

54
Q

Bunyaviruses–RNA structure

A
  • SS - circular
    • 3 segments
55
Q

Bunyaviruses–capsid symmetry

A
  • helical
56
Q

Bunyaviruses–medical importance

A
  • California encephalitis
    • arbovirus, arthropod borne (mosquitoes, ticks)
  • Sandfly/Rift Valley fevers
    • arbovirus, arthropod borne (mosquitoes, ticks)
  • Crimean Congo hemorrhagic fever
    • arbovirus, arthropod borne (mosquitoes, ticks)
  • Hantavirus–hemorrhagic fever, pneumonia
57
Q

Delta virus–envelope

A

YES

58
Q

Delta virus–RNA structure

A
  • SS - circular
59
Q

Delta virus–capsid symmetry

A
  • uncertain
60
Q

Delta virus–medical importance

A
  • HDV is a “defective” virus that requires the presence of HBV to replicate
61
Q

Negative stranded viruses–properties and name the 6 viruses

A
  • most transcribe - strand to +
  • virion brings its own RNA dependent RNA polymerase
  • includes:
    • Arenaviruses
    • Bunyaviruses
    • Paramyxoviruses
    • Orthomyxoviruses
    • Filoviruses
    • Rhabdoviruses
      • “Always Bring Polymerase Or Fail Replication”
62
Q

name the 4 segmented viruses

A
  • all are RNA viruses
    • Bonyaviruses
    • Orthomyxoviruses (influenza viruses)
    • Arenaviruses
    • Reoviruses
      • “BOAR”
63
Q

name the 5 Picronaviruses

A
  • Poliovirus
  • Echovirus
  • Rhinovirus
  • Coxsackievirus
  • HAV
    • “PicoRNAvirus = small RNA virus”
    • “PERCH on a ‘peak’” (pico)
64
Q

properties of Picornaviruses

A
  • RNA is translated into 1 large polypeptide that is cleaved by proteases into functional viral proteins
  • all are enteroviruses (fecal-oral spread) except rhinovirus
65
Q

what can Picornavirus cause?

A
  • aseptic (viral) meningitis (except rhinovirus and HAV)
66
Q

properties of Rhinovirus

A
  • a picornavirus
  • nonenveloped RNA virus
  • >100 serologc types
  • acid labile–destroyed by stomach acid; therefore, does not infect the GI tract (unlike other picronaviruses)
67
Q

what does rhinovirus cause?

A
  • common cold
    • “Rhino has a runny nose”
68
Q

properties of Yellow Fever virus

A
  • flavivirus (also an arbovirus) transmitted by Aedes mosquito
  • virus has a monkey or human reservoir
  • may see Councilman bodies (eosinophilic apoptotic globules) on liver biopsy
69
Q

Yellow fever virus–symptoms

A
  • high fever
  • black vomitus
  • jaundice
    • “flavi” = yellow, jaundice
70
Q

properties of rotavirus

A
  • segmented dsRNA virus (a reovirus)
  • villous destruction with atrophy leads to dec absorption of Na+ and loss of K+
71
Q

what is rotavirus the most important global cause of?

A
  • infantile gastroenteritis
72
Q

what does rotavirus cause?

when is it common, and where?

A
  • major cause of acute diarrhea in the US
    • “ROTAvirus = Right Out The Anus”
  • during winter
  • especially in day care centers, kindergartens
73
Q

what is recommended for infants regarding rotavirus?

A
  • CDC recommends routine vaccination of all infants
74
Q

properties of influenza viruses

A
  • orthomyxoviruses
    • enveloped
      • ssRNA viruses with 8 segment genome
  • contain hemagglutinin (promotes viral entry) and neuraminidase (promotes progeny virion release) antigens
75
Q

what are patients with orthomyxovirus at risk of?

A
  • patients at risk for fatal bacterial superinfection
    • most commonly S. aureus, S. pneumoniae, H. influenzae
76
Q

reformulated vaccine for influenza virus

A
  • reformulated vaccine (“the flu shot”) contains viral strains most likely to appear during flu season, due to the virus’ rapid genetic change
77
Q

what type of vaccine is most often used for the flu shot?

A
  • killed viral vaccine
78
Q

live attenuated virus for influenza virus

A
  • contains temperature sensitive mutant that replicates in the nose but not in the lung
    • administered intranasally
79
Q

genetic shift/antigenic shift

A
  • causes pandemics
  • reassortment of viral genome segments, such as when segments of human flu A virus reassort with swine flu A virus
80
Q

genetic drift/antigenic drift

A
  • causes epidemics
  • minor (antigenic drift) changes based on random mutation in hemagglutinin or neuroaminidase genes
81
Q

genetic drift vs. shift

A
  • Suddent Shift is more deadly than gradual Drift
82
Q

rubella virus

A
  • togavirus
    • causes rubella, once known as German (3 day) measles
83
Q

rubella virus–symptoms

A
  • fever
  • postauricular and other lymphadenopathy
  • arthralgias
  • fine, confluent rash that starts on face and spreads centrifugally to involve trunk and extremities
84
Q

rubella virus–congenital

A
  • causes mild disease in children but serious congenital disease (a ToRCHeS infection)
    • congenital rubella findings include “blueberry muffin” appearance due to dermal extramedullary hematopoiesis
85
Q

what does Paramyxoviruses cause?

A
  • cause disease in children
    • include those that cause
      • parainflueza: croup–seal like barking cough
      • mumps
      • measles
      • RSV: causes respiratory tract infection–bronchiolitis, pneumonia
        • in infants
86
Q

properties of Paramyxoviruses

A
  • all contin surface F (fusion) protein, which causes respiratory epithelial cells to fuse and form multinucleated cells
87
Q

what prevents pneumonia caused by RSV infection in premature infants?

A
  • Palivizumab
    • monoclonal antibody against F protein
88
Q

Croup (acute laryngotracheobronchitis)

A
  • caused by parainfluenza viruses (paramyxovirus)
  • results in:
    • “seal like” barking cough
    • inspiratory stridor
  • narrowing of upper trachea and subglottis leads to characteristic steeple sign on x-ray
89
Q

what can cause severe croup cause?

A
  • severe croup can result in pulsus paradoxus secondary to upper airway obstruction
90
Q

Measles (rubeola) virus–presentation

A
  • a paramyxovirus that causes measles
  • presentation:
    • prodromal fever with cough
    • coryza
    • conjunctivitis
      • “3 C’s of measles: Cough, Coryza, Conjunctivitis”
    • Koplik spots–bright red spots with blue white centers on buccal mucosa (A)
      • followed 1-2 days later by a maculopapular rash (B) that starts at the head/neck and spreads downward
    • Lymphadenitis with Warthin-Finkeldey giant cells (fused lymphocytes) in a background of paracortical hyperplasia
91
Q

Measles virus–possible sequelae

A
  • SSPE–subacute sclerosing panencephalitis, occurring years later
  • encephalitis (1:2000)
  • giant cell pneumonia–rarely, in immunocompromised
92
Q

Measles virus and Vitamin A

A
  • vitamin A supplementation can reduce morbidity and mortality from measles, particularly in malnourished children
93
Q

mumps virus

A
  • paramyxovirus that causes mumps
  • symptoms:
    • Parotitis (A)
    • Orchitis (inflammation of testes)
    • aseptic Meningitis
    • Pancreatitis
      • “Mumps make your parotid glands and testes as big as POM-Poms”
94
Q

why is mumps uncommon?

A
  • due to effectiveness of MMR vaccine
95
Q

what can mumps cause especially after puberty?

A
  • can cause sterility
96
Q

properties of Rabies virus

A
  • bullet shaped virus (A)
  • negri bodies–cytoplasmic inclusions (B)
    • commonly found in Purkinje cells of cerebellum and hippocampal neurons
  • travels to CNS by migrating in a retrograde fashion up nerve axons after binging to ACh receptors
97
Q

Rabies–incubation and prophylaxis

A
  • rabies has long incubation period (weeks to months) before symptoms onset
  • postexposure prophylaxis is wound cleaning plus immunization with killed vaccine and rabies immunoglobulin
    • example of passive-active immunity
98
Q

Rabies–progression

A
  • fever
  • malaise –> agitation
  • photophobia
  • hydrophobia
  • hypersalivation –> paralysis
  • coma –> death
99
Q

Rabies–transmission

A
  • more commonly from bat, raccoon, and skunk bites that from dog bites in the US
  • aerosol transmission (ie. bat caves) also possible
100
Q

properties of Ebola virus

A
  • filovirus
  • targets endothelial cells, phagocytes, hepatocytes
101
Q

Ebola virus–incubation and presentation

A
  • presents following an incubation period of up to 21 days
  • presentation:
    • abrupt onset of flu like symptoms
    • diarrhea/vomiting
    • high fever
    • myalgia
102
Q

Ebola virus–what can it progress to?

A
  • can progress to:
    • DIC
    • diffuse hemorrhage
    • shock
103
Q

Ebola virus–diagnosis

A
  • diagnosed with RT-PCR within 48 hours of symptoms onset
  • high mortality rate
104
Q

Ebola virus–transmission

A
  • requires direct contact with:
    • bodiy fluids
    • fomites (including dead bodies)
    • infected bats or primates (apes/monkeys)
  • high incidence of nosocomial infection
105
Q

Ebola virus–treatment and prevention of transmission

A
  • supportive care
    • no definitive treatment
  • strict isolation of infected individuals and barrier practices for health care workers are key to preventing transmission

USMLE Step I Microbiology (44 decks)

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