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Infectious Diseases > Influenza > Flashcards

Influenza Flashcards

1
Q

What is the etiological agent of influenza

A

Orthomyxovirus

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2
Q

Describe the etiological agent of influenza

A

spherical or filamentous particle, helical nucleocapsid, enveloped, has 6-8 different segments that codes for 1-2 proteins each

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3
Q

what does orthomyxovirus mean

A

Correct mucus, virions bind to mucoproteins

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4
Q

what are the distinctive characteristics of influenza virus

A

replicates in the nucleus, undergoes reassortment by exchanging genome segments b/t strains, and reassortment generates new viruses that cause pandemics due to changed surface antigens

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5
Q

How many types of influenza viruses are there

A

3

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6
Q

what are the different types of influenza viruses

A

Influenza A, B, and C

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7
Q

describe Influenza A

A

Found in humans, swine, avian, equine, and marine mammals. may cause large pandemics. Significant morbidity and mortality

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8
Q

Describe Influenza B

A

Only found in Humans. Not associated with pandemics/ only epidemics. Cause mild disease

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9
Q

Describe Influenza C

A

Found in humans and swine. not associated with pandemics and cause mild disease

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10
Q

The major host for Influenza A is what

A

Wild Ducks

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11
Q

Hemagglutinin serves as what in Influenza

A

It is a major surface antigen that serves as site of attachment to host cell and initiates infection

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12
Q

How many HAs have been identified

A

15 antigenically distinct HAs (H1-H15)

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13
Q

what does HA stand for

A

Hemagglutinin

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14
Q

Which HAs have been identified for human influenza A

A

H1,H2, and H3

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15
Q

What purpose does Neuraminidase serve during Influenza

A

It is a major surface antigen that acts as an enzyme that cleaves sialic acid from glycoproteins

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16
Q

What major role does NA play in infection

A

Is important during the replication (maturation) of virus

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17
Q

What does NA stand for

A

Neuraminidase

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18
Q

How many NAs have been identified

A

9 antigenically distinct NAs

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19
Q

Which NAs have been identified for human influenza A

A

N1 and N2

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20
Q

What unique feature of influenza A explains why it causes major epidemic and pandemic diseases in humans

A

The frequency with which they can change antigenically, Antigenic variation

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21
Q

What are the two degrees of an antigenic variation

A

Drift and shift

22
Q

When there is a small change antigenically, its called

A

a drift

23
Q

when there is a major change antigenically, its called

A

a shift

24
Q

Briefly describe an Antigenic Drift

A

minor changes that occur every year that are associated with variation in HA that cause epidemics. Epidemics occur on avg every 2.4 yrs

25
Q

Briefly describe an Antigenic Shift

A

Major changes in HA and NA that produce a new virus strain that the population has no herd immunity for and results in pandemic. These are unpredictable but occur every 10 to 12 yrs

26
Q

Describe the genome of Influenza A

A

consists of 8 distinct segmented pieces of single-stranded RNA. 4 pieces encodes for HA and 6 encodes for NA.

27
Q

How does the new strains or variations occur

A

When two unrelated viruses infect the same cell, 16 RNA segments are released and genetic reassortment may yield progeny virus

28
Q

How is Influenza transmitted

A

the virus spreads by respiratory droplets and may be involved in transmission

29
Q

How long can the virus remain infectious in environment

A

Virus remains infectious for >24 hrs after aerosolization and 1-2 days on hard nonporus surfaces

30
Q

Describe the Pathogenesis of Influenza

A

Initial site of infections is the respiratory tract mucosa and shedding begins ~1 day before onset of illness which presents abruptly with prominent systemic illness and respiratory syndromes. Virus induced cytopathology and apoptosis contributes to illness. Shedding last 3-7 days. Fever and systemic complaints end on day 7. Slow recovery w/ cough and malaise last for 2-4 weeks

31
Q

What usually causes death with Influenza

A

Pulmonary complications such as secondary bacterial infection, excessive expression of cytokines (cytokine storm), or excessive hemorrhaging when lungs are more involved and could drown and suffocate

32
Q

How many people die in the US from Influenza

A

36k each year ranging from 17-52k

33
Q

Influenza is usually associated with a ______ epidemic curve and mortality is generally highest in ________

A

U-shaped; young and older adults

34
Q

How long does it take Influenza to infect you?

A

1- 5 days

35
Q

Excess morbidity and mortality are particularly high in who

A

Those with cardiovascular or pulmonary conditions, chronic metabolic disease, or HIV/AIDS

36
Q

Death rates are as high as __ per year in nursing home residents

A

2.8%

37
Q

How is Influenza treated

A

Four antiviral drugs available ; Amantadine, Rimantadine, Zanamivir, and Oseltamivir (Tamaflu)

38
Q

When is the antiviral therapy shown to be non beneficial

A

after 48 hrs or more after appearance of clinical symptoms

39
Q

When is treatment most beneficial

A

When its started in the first 24 hrs of clinical symptoms

40
Q

How does amantadine and rimantadine take action

A

they prevent the uncoating of virus

41
Q

How does zanamivir and oseltamivir take action

A

they prevent maturation of virus

42
Q

Briefly describe the mechanism of action for Amantadine

A

It targets the M2 (channel) protein of virus by blocking the entry of H+ inons into virion and thereby prevents the release of RNA/nucleoprotein complexes into cytoplasm

43
Q

briefly describe the mechanism of action for Zanamivir and Oseltamivir

A

It competes with sialic acid for binding to NA preventing sialic acid cleavage and prevent the release of virus

44
Q

Are there any vaccines for Influenza

A

There is a Live attenuated vaccine that induces mucosal immune responses (IgA) that closely mimics natural response and a killed vaccine that is grown in chicken eggs and contain influenza subtypes A and B

45
Q

The first epidemic of Influenza was described in _____

A

Europe in 1510

46
Q

What were the names of Influenza in the 16th Century

A

the new acquaintance and the gentle correction

47
Q

What were the names of Influenza in the 17th Century

A

The new delight, the jolly rant, and la grippe

48
Q

What were the names of Influenza in the 18th Century

A

the influenza and Influenza

49
Q

When did the great influenza Pandemic occur

A

1918-1919

50
Q

_____ persons died worldwide with a fatality rate of _____ worldwide during the pandemic

A

20-100 million ; 4-20%

51
Q

Influenza has killed more persons in __ than ____ has killed in ____ and accounted for ___ of US war deaths

A

one year; HIV/AIDS; 28 years; 80%

52
Q

The Great Influenza Pandemic came in 4 waves which were

A

1st wave Jan. 1918, 2nd wave Aug. 1918 (most virulent), 3rd wave Dec. 1918, and ended Mar. 1919

Infectious Diseases (9 decks)

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