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Bio 3021 Infectious Disease & Society > Influenza > Flashcards

Influenza Flashcards

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1
Q

Meaning of Orthomyxovirus

A

ortho: correct or normal
myxa: mucus
virions bind to mucoproteins

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2
Q

Virion components for Influenza

A

compact helical nucleocapsid

envelope derived from plasma membrane

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3
Q

Genome components for influenza

A

linear ss RNA, negative sense
6-8 dif segments
each gene segment codes for 1 or 2 proteins

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4
Q

(3) Distinctive Characteristics of orthomyxovirus

A

replicates in the nucleus, unlike most RNA virus
undergoes reassortment by exchanging genome segments between strains
reassortment generates new viruses that cause pandemic due to changed surface antigens

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5
Q

How many influenzas are there?

A

3; influenza A, influenza B, influenza C

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6
Q

Influenza A?

A

may cause large pandemics
significant morbidity & mortality
humans, swine, avian, marine mammals

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7
Q

Influenza B?

A

Humans only
not associated w/pandemics
mild disease

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8
Q

Influenza C?

A

Humans & Swine
not associated w/pandemics
mild disease

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9
Q

Influenza A major surface antigens?

A

Hemagglutinin (HA)

Neuraminidase (NA)

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10
Q

Hemagglutinin (HA)?

A

major surface antigen
serves as site of attachment to host cell
initiates infection

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11
Q

How many antigenically distinct HAs have been identified?

A

15; H1 to H15

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12
Q

How many antigenically distinct HAs have been identified for human influenza A?

A

3; H1 to H3

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13
Q

Neuraminidase (NA)?

A

major surface antigen
enzyme that cleaves sialic acid from glycoproteins
plays a major role in replication of virus

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14
Q

How many antigenically distinct NAs have been identified for influenza A?

A

9; N1 to N9

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15
Q

How many antigenically distinct NAs have been identified for human influenza A?

A

2; N1 to N2

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16
Q

What is a unique feature of influenza A?

A

frequency with which they can change antigenically

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17
Q

_____ explains why influenza A viruses cause major epidemic & pandemic diseases in humans

A

antigenic variation

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18
Q

What does antigenic variation involve? result in?

A

involve HA and NA

result in antigenic drift & antigenic shift

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19
Q

(4) Characteristics of Antigenic Drift

A

Relatively minor changes that occur approximately every year
Associated with antigenic variation (mutation) in HA
Antigenic variation in HA results in an epidemic
Epidemics occur on average every 2.4 years

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20
Q

(4) Characteristics of Antigenic Shift

A

Major changes in HA and NA produce “new” virus strain
The overall population has no herd immunity to new strain
Antigenic variation in both HA and NA results in a pandemic
Pandemics are unpredictable, but occur every 10 to 12 years

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21
Q

Genome of influenza A consists of ____

A

segmented genome

8 distinct pieces of ss RNA

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22
Q

RNA segment ____ encode for HA; RNA segment ____ encodes for NA

A

4;6

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23
Q

What happens when 2 unrelated viruses infect the same cell?

A

16 RNA segments are relased

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24
Q

2 influenza A+ 1 influenza B=

A

Trivalent

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25
Q

How is influenza spread?

A

By respiratory droplets

26
Q

The human infectious dose is ______ infectious virus particles, and the virus remains infectious for _____ after aerosolization. Retains infectivity on hard nonporous surfaces for ______. ____ may be involved in transmission.

A

1-5; 24 hrs

27
Q

(6) Describe the pathogenesis of influenza.

A
  1. initial site of infection is the respiratory tract mucosa
  2. Virus shedding begins ~1 day before onset of illness
  3. Systematic illness and respiratory syndrome present abruptly
  4. Duration of shedding is gen 3-7 days
  5. Fever & systemic complaints usually after 7 days
  6. Recovery is slow
28
Q

What do the complications of influenza include?

A

pneumonia & acute central nervous system manifestations

29
Q

Death is usually due to pulmonary complications

A

secondary bacterial infection
excessive expression of cytokines
excessive hemorrhage

30
Q

How many die on avg each year from seasonal influenza?

A

36,000 persons

31
Q

Mortality is generally highest in______

A

young and among older adults

32
Q

Excess morbidity & mortality highest in persons with?

A

cardiovascular conditions
asthma
renal dysfuntion
HIV/AIDS

33
Q

How many antiviral drugs are currently available for prevention and treatment of influenza? When is the greatest benefit?

A

4 (amantadine, rimantadine, zanamivir, TAMAFLU)

started within the first 24 hours

34
Q

What are the 2 mechanisms of action?

A

uncoating & preventing maturation

35
Q

Which drugs mechanism of action is uncoating of virus?

A

Amantadine & Rimantadine

36
Q

Which drugs mechanism of action is preventing maturation of virus?

A

Zanamivir & Oseltamivir (tamaflu)

37
Q

Where are inhibitors of uncoating most useful?

A

Nursing homes

38
Q

What is the target for amantadine & rimantadine?

A

M2 protein of virus

39
Q

Mechanism for uncoating

A

antivirals blocks channel formed by M2 protein, prevents entry of H+ ions into the virion, and thereby prevents release of RNA/nucleoprotein complexes into cytoplasm

40
Q

(3) What are the purposes of the M2 protein of the virus?

A

Forms transmembrane channels that allow H+ ions to enter interior of virion during acidification within endosome
Weakens interaction between matrix protein M1 and nucleocapsids
Facilitates release of nucleocapsids into cytoplasm

41
Q

Mechanism for preventing maturation

A

antivirals are designed to compete more favorably with sialic acid for binding to NA, prevent sialic acid cleavage, and thereby prevent release of virus

42
Q

What is the target for zanamivir & tamaflu?

A

neuraminidase

43
Q

Inactivated killed vaccines (trivalent) used for influenza?

A

virus grown in chicken eggs, purified, and formalin-inactivated
protection about 70%-90% when good antigenic match

44
Q

Live-attenuated vaccines used for influenza?

A

replicate efficiently at low temps
induce mucosal immune response (IgA)
use of nasal rather than parental route of admin more acceptable to pts

45
Q

When and where was the first description of an influenza?

A

Europe 1510

46
Q

In 16th century known as (2)

A

“the new acquaintance”

“the gentle correction”

47
Q

In 17th century known as (3)

A

“the new delight”
“the jolly rant”
“la grippe”

48
Q

In 18th century known as (1)

A

“the influence”— INFLUENZA

49
Q

The Great Influenza Pandemic of 1918-1919

A

20-100 million ppl died worldwide in one year
Spanish press was first to report on the disease (known as the Spanish Flu)
pandemic involved 3 waves of virus infection

50
Q

First Wave of GIP of 1918-1919 (jan)

A

not more dangerous than previous influenza pandemics

deaths primarily among infants & elderly

51
Q

Second Wave of GIP of 1918-1919 (aug)

A

Extremely virulent virus appeared in three locations
High mortality rate in infants
High mortality rate in persons 20 - 40 years of age

52
Q

Third Wave of GIP of 1918-1919 (dec)

A

Less virulent than the second wave virus

Same high incidence of death in persons 20 - 40 years of age

53
Q

When did the GIP end?

A

March 1919

54
Q

What did the lung tissues of victims of 1918-1919 pandemic show?

A

Virus RNA contained sequences of swine influenza virus

55
Q

1976 Swine Influenza Scare?

A

swine influenza virus isolated from fatal case of influenza in NJ & farmer and pig in Wisconsin
National Immunization Program against swine influenza, so rapid development of vaccine administered in 45 million persons
Swine influenza virus never entered the general population

56
Q

What disease developed 4 to 6 weeks after vaccination during the 1976 swine influenza scare?

A

Guillain-Barre

57
Q

2009 Swine Influenza Pandemic?

A

Outbreak of H1N1 influenza virus with genetic elements of swine influenza virus (possibly avian influenza virus) during summer months

58
Q

Severe/Fatal disease of H1N1 highest in persons aged? Mortality?

A

20-40 years

far below 1918-1919 pandemic

59
Q

The H1N1 influenza virus was resistant to which antiviral drug?

A

Tamaflu (Oseltamivir)

60
Q

Influenza is caused by?

A

A tiny living poisonous plant

Bio 3021 Infectious Disease & Society (4 decks)

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