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Influenza virus Flashcards

1
Q

To chich virus family do influenza viruses belong?

A

Orthomyxoviridae

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2
Q

Mention the three types of influenza viruses.

A

A, B, and C

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3
Q

What are the common structural features of all three influenza virus types?

A
  • Host-cell-derived envelope
  • Envelope glycoproteins for entry and exit
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4
Q

What type of nucleic acid do influenza viruses have?

A

Segmented (8 segments), negative-sense, single-stranded RNA

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5
Q

How are influenza A subtypes classified?

A

Based on two antigens:
* Hemagglutinin (H or HA)
* Neuraminidase (N or NA)

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6
Q

What are two common influenza A subtypes?

A

H1N1 and H3N2

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7
Q

T/F. Influenza virus are enveloped.

A

True

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8
Q

This is an attachment protein of the virus. Has the receptor binding site.

A

Hemagglutinin

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9
Q

This is an enzyme thar removes terminal sialic acids from glycoproteins. Helps the virus exit infected cells and spread to new ones.

A

Neuraminidase

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10
Q

What is the function of the M2 protein in influenza viruses?

A

Integral membrane protein (ion channel)

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11
Q

What is the function of the matrix (M1) protein in influenza viruses?

A
  • Provides structural support to the virion
  • Plays a key role in virus assembly
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12
Q

What proteins are bound to each RNA segment in influenza viruses?

A
  • Nucleoprotein (NP)
  • Polymerase proteins (PB1, PB2, PA)
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13
Q

What are the two non-structural proteins found in influenza-infected cells?

A

NS1 and NS2 (NEP)

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14
Q

What does HA bind to on the host cell membrane?

A

Sialic acid-containing receptors

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15
Q

What is the role of the M2 protein in influenza virus uncoating?

A
  • Acts as an ion channel
  • Allows H+ to enter the virion, facilitating uncoating
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16
Q

Where are influenza viral gene segments transported after entry into the host cell?

A

To the nucleus

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17
Q

What is the function of the polymerase complex (PB1, PB2, PA) in influenza replication?

A

It synthesizes positive-sense mRNA and negative-sense genomic RNA

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18
Q

What effect does the influenza virus have on host cell protein synthesis?

A

It disrupts host cell protein synthesis

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19
Q

What process allows influenza viruses to produce different viral proteins from mRNAs?

A

Splicing of mRNAs

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20
Q

Fro where do influenza virions bud during their release from the host cell?

A

Lipid rafts on the cell surface

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21
Q

What viral proteins are incorporated into the envelope of newly budded influenza virions?

A

HA, NA, and M2

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22
Q

T/F. Influenza viruses are regularly associated with excess morbidity and mortality.

A

True

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23
Q

Which influenza subtype is associated with the highest excess mortality?

A

H3N2, but H1N1 also contributes

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24
Q

What factors likely contributed to the decline in pneumonia and influenza hospitalizations from 1996 to 2011?

A

Vaccination

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25
Which age group has the highest attack rates of influenza?
Young individuals
26
Which age group has the highest mortality rates from influenza?
Older adults, especially those over 65
27
Which age group of children is most affected by influenza?
Younger than 2 years
28
What are common secondary complications of influenza in children?
Otitis media and pneumonia
29
An outbreak of influenza confined to a specific location (city, town, or country). This can be defined as...
Influenza epidemic
30
When do influenza epidemics occur in temperate climates?
* North: November to April * South: May to September
31
What environmental factors contribute to influenza epidemic seasonality?
Temperature and humidity
32
What behavioral factors may increase influenza transmission in colder months?
Indoor crowding and school attendance
33
What are the three primary modes of influenza transmission?
* Aerosol transmission * Droplet transmission * Surface contamination
34
These are caused by the emergence of an antigenically variant influenza virus, to which the population has little or no prior immunity.
Pandemic
35
It refers to the frequent changes in the antigenicity of the influenza virus.
Antigen variation
36
Antigenic variation mainly involves changes in which two glycoproteins?
HA and NA
37
This refers to minor antigenic changes that occur frequently within the HA and/or NA. Causes epidemics.
Antigenic drift
38
What part of the influenza virus is primarily affected by antigenic drift?
Hemagglutinin
39
What causes antigenic drift in influenza viruses?
Gradual accumulation of amino acid changes
40
T/F. Antigenic drift reduces neutralization by antibodies generated against previous strains.
True
41
It refers to major antigenic changes in the HA and/or NA of influenza A viruses. Caused by reassortment between two different strains of influenza viruses. Causes pandemics.
Antigen shift
42
What is the result of an antigenic shift in influenza A viruses?
A new influenza virus (HxNx) enters the population, often leading to a pandemic
43
What is the incubation period for influenza?
1-2 days
44
What are the systemic symptoms of influenza?
Feverishness, chills, headache, myalgia, malaise anorexia, and sometimes prostration
45
In children, where is myalgia (muscle pain) particularly prominent?
The calf muscles
46
What eye-related symptoms can occur in influenza?
Severe eye muscle pain with lateral gaze, tearing, and burning
47
What are the primary respiratory symptoms of influenza?
Dry cough, sever pharyngeal pain, and nasal obstruction or discharge
48
What are the common physical exam findings in influenza?
* Toxic appearance early in illness * Flushed face, hot and moist skin * Watery, reddened eyes * Clear nasal discharge * Hyperemic mucous membranes * Small, tender cervical lymph nodes
49
What are the three main types of pneumonia associated with influenza?
* Primary influenza viral pneumonia * Secondary bacterial pneumonia * Mixed viral and bacterial pneumonia
50
What are some milder pulmonary syndromes that can occur with influenza?
* Tracheobronchitis * Localized viral pneumonia
51
Which individuals are at hichest risk for primary influenza viral pneumonia?
Those with cardiovascular disease
52
What are the key symptoms of primary influenza viral pneumonia?
Fever, cough, dyspnea, and cyanosis
53
What do chest radiographs show in primary influenza viral pneumonia?
* Bilateral findings consistent with adult respiratory distress syndrome (ARDS) * No consolidation
54
What do blood gas studies show in primary influenza viral pneumonia?
Marked hypoxia
55
What are the hallmark symptoms of secondary bacterial pneumonia?
Cough, sputum production, and signs of consolidation
56
What are the three most common pathogens causing secondary bacterial pneumonia after influenza?
* Streptococcus pneumoniae * Staphylococcus aureus * Methicillin-resistant S. aureus (MRSA) * Haemophilus influenzae
57
Where does the influenza virus attach and penetrated in the respiratory tract?
Columnar epithelial cells
58
What three factors can block influenza virus attachment?
* IgA * Mucoproteins * Mucociliary apparatus
59
How does influenza inhibit host-cell protein synthesis?
* Degradation of newly synthesized cellular mRNAs by endonuclease * Blocking translation of cytoplasmic mRNAs
60
What viral protein contributes to protein degradation and cell death in influenza-infected cells?
PA protein
61
What are the two primary mechanisms of cell death in influenza virus infection?
Necrosis and apoptosis
62
In which respiratory cells does apoptosis commonly occur in influenza virus infection?
Bronchiolar and alveolar epithelial cells
63
What viral factor induces apoptosis by poisoning mitochondria in influenza virus infections?
PB1-F2 protein of influenza A
64
How is the Fas antigen involved in apoptosis during influenza virus infection?
Induced by double-stranded RNA during replication, triggering apoptosis
65
T/F. Influenza virus cause a productive infection in peripheral blood mononuclear cells (PBMCs)?
False
66
What cellular defects occur due to influenza infection in PBMCs?
* Defects in chemotaxis and phagocytosis * Decreased proliferation and costimulation
67
What are the bronchoscopic findings in typical acute influenza?
Diffuse inflammation of the larynx, trachea, and bronchi with mucosal injection and edema
68
Key histological findings in influenza biopsies.
* Vacuolization of columnar cells with cell loss
69
How do individual cells appear histologically in influenza infection?
Shrinkage, pyknotic nucleus, and loss of cilia
70
T/F. Most influenza cases are diagnosed based on clinical symptoms and seasonal epidemiology.
True
71
Most widely used method for diagnosing influenza virus.
PCR
72
This test detects viral antigens in respiratory secretions.
Rapid influenza diagnostic tests
73
What are some drugs used to treat influenza?
* Oseltamivir * Zanamivir * Perimivir

Infectious diseases pathophysiology (13 decks)

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