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Infection 2023 > Influenza > Flashcards

Influenza Flashcards

(50 cards)

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1
Q

What are viruses?

A

Simple structures
Delivery and Payload system

Delivery system protects virus and binds to target cells

Payload contains genome and enzymes needed to initiate replication

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2
Q

Influenza summary

A 
Infection of respiratory tract (nose, mouth, throat, bronchial tubes and lungs)
Highly infectious (closed communities especially)
Most 8-10 week period in winter
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3
Q

Structure influenza

A

Orthomyxovirus - spherical
enveloped
segmented -ve ssRNA

  • 3 RNA polymerases (high error rate)
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4
Q

Outside structure influenza

A

Haemagglutinin (H) antigen - binds to cells of infected person

Neuraminidase (N) antigen - releases virus from host cell surface

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5
Q

1 segment of influenza =

A

1 polypeptide

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6
Q

Types of influenza and what species

A

A - humans, swine, equine, birds, marine mammals
B - humans
C - humans and swine

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7
Q

Influenza A involves

A

Antigenic shift AND drift
May cause large pandemics
Significant mortality for young people

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8
Q

Influenza B involves

A

Antigenic drift ONLY

Severe disease = old adults or high risk (no pandemics)

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9
Q

Influenza C involves

A

Antigenic drift ONLY

Mild disease, no seasonality

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10
Q

Most concern influenza type

A

Influenza A -
outbreaks most years
epidemics and pandemics
live and multiply in many animals (wildfowl in particular)

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11
Q

Second concern influenza type

A

Influenza B
Smaller outbreaks, less disease
Humans only
Mostly children affected

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12
Q

How does influenza replicate

A

-ve ssRNA –> +ve ssRNA
via RNA dependent RNA polymerase
–>
this produce mRNA which can make viral proteins

-ve —> +ve —> -ve produces multiple -ve ssRNA copies

these then assemble in nucleocapsid = replicated

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13
Q

How is influenza virus transmitted? 3 modes

A

Respiratory route (cough sneeze inhale)

  • small particle aerosols <10micrometre (remain in air)
  • larger particle/droplets
  • viral particles (land on surface, indirect)
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14
Q

Barriers to influenza

A

Resp epithelium = thick glycocalyx and mucus
Trap virus particles

Ciliated epithelium sweep mucus up to be swallowed (mucociliary escalator)

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15
Q

Immunological defences lung

A

Secretory IgA
Natural killer cells
Macrophages

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16
Q

How does virus enter cell?

A

Neu5Ac (NANA) residues act as receptor for Hemagglutinin antigen on virus
Invagination of virus
into Endocytosis vesicle
release virion into cytoplasm

(RECEPTOR MEDIATED ENDOCYTOSIS)

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17
Q

What is a NANA residue?

A

Sialic acid on glycoprotein/glycolipid which acts as receptor for influenza virus

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18
Q

How does virus leave cells?

A

Hemogglutinin is already attached to NANA sialic acid receptor
Neuraminidase cleaves glycoprotein + sialic receptor NANA off and allows virus to leave

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19
Q

Complications of influenza

A

Meningitis/encephalitis
Otitis media (ear infection)
Croup (young children usually)
Pneumonia

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20
Q

Time course influenza

A

Incubation - 1-5 days

Recovery time - 2-7 days

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21
Q

When can virus be found in resp secretions after initial infection?

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A

As soon as 24 hours after infection

22
Q

Those at risk of serious influenza complications

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A 
Children under 6 months
Older people (65+)
Underlying health conditions (resp, cardiac)
Pregnant women 
Obesity (morbid >40BMI)
23
Q

Flu during pregnancy

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A

Perinatal mortality
Prematurity
Smaller neonatal size/lower birth weight

24
Q

Diagnosing infuenza

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A

usually from symptoms and clinical assessment
BUT can do:
Rapid influenza diagnostic tests
PCR

25
Treatments influenza
Antivirals Neuraminidase inhibitors prevention: Vaccines
26
Antivirals example and explain
Rimantadine & Amantadine Inhibit viral uncoating after uptake through M2 protein for Influenza A
27
Neuraminidase inhibitors example and explain
Oseltamivir (Tamiflu) & Zanamivir (Relenza) Inhibit viral release from cells (cant cleave off) and cause aggregation of particles for influenza A AND B
28
Vaccines for flu
Both for Influenza A AND B: Formalin inactivated vaccine injection (quadri/trivalent) Live, attenuated, cold adapted vaccine NASAL SPRAY (quadrivalent, for children)
29
What does cold-adapted vaccine mean?
Will only stay in upper resp tract | Cannot survive in lungs as too warm
30
What does trivalent and quadrivalent mean?
Trivalent - contains 2 Influenza A strains and 1 B strain Quadrivalent - contains 2 influenza A strains and 2 influenza B strains
31
Neuraminidase inhibitors (TAMIFLU) come from
Chinese Star anise: | Shikimic acid
32
Genetic changes influenza (antigenic drift)
Life cycle = 6 hours Constantly replicating Viral RNA polymerase = high error rate, lack of proofreading = mutations
33
What happens as a result of these mutations?
Genetic resistance and variation
34
What is antigenic drift?
``` Minor changes (natural mutations) in genes of flu virus that occur gradually over time Minor antigenic changes in H and N Cause seasonal epidemics ``` NO VIRAL SUBTYPE CHANGE
35
How does antigenic drift affect vaccines?
WHO monitors epidemiology and makes recommendations about strains likely to be circulating Results in composition of virus vaccines
36
How do PHE help with flu?
Send letters to GP's with updates (strains, no. of cases) and details of WHO recommendations
37
Other genetic changes influenza (antigenic shift)
``` Dramatic changes in antigenic H and N properties Infrequent (10-20 years) ONLY Influenza A Change subtype (H1N1 --> H3N2) Surface antigens from different species ```
38
Antigenic shift defined
Major changes in genes that occur suddenly when two or more different strains combine This results in NEW subtype = widespread epidemics/pandemics
39
How can antigenic shift happen?
Influenza viruses from different species combine in same host at same time Reassortment of RNA segments from each species into new capsid
40
Why can antigenic shift occur in Influenza A?
Can infect many animals - horses, pigs, waterfowl Host infected with two different subtypes influenza (eg pig can be infected by human and avian specific viruses) Reassortment of 2 different specie virus in one host Has potential to spread among humans, birds and pigs
41
Consequences antigenic shift
New subtype not seen before = no immunity defence Pandemics and epidemics
42
Epidemic
Widespread occurrence of infectious disease in a community at particular time
43
Pandemic
Epidemic over a very large area; populations all over the world
44
Major Influenza type A outbreaks
Spanish influenza (1918 - human and avian H1N1) Asian influenza (1957 - human and avian reassortment H2N2) Hong kong influenza (1968 - human and avian components H3N2) 2009 Novel H1N1 (human swine and avian reassortment)
45
Spanish influenza truth
Was actually from Kansas | But spain only place neutral in WW1 and was able to report news on flu and not on war
46
Spanish flu size
50 million | more people died (1 year) than in 4 years of black death
47
How does flu kill people? (2 methods)
1: Immune system overreacts T cells attack and destroy tissue of virus - particularly lungs 2: Opportunistic secondary infection (eg streptococcus/staphylococcus) in lungs usually
48
Why do we get symptoms?
body's immune response to viral invasion Antibodies triggered and immune cells move to site of infection Release cytokines = local inflammation
49
What can occur when encountering new subtype of infleunza?
Cytokine storm (bird flu jumped species)
50
Who does WHO recommend flu vaccine for?
``` Pregnant women children 6months - 5 years elderly (>65) people with chronic medical condition healthcare workers ```

Infection 2023 (29 decks)

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