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Infection Diseases > Influenza > Flashcards

Influenza Flashcards

1
Q

Structure of influenza virus

A
  • Spherical, enveloped viruses containing a segmented, negative strand RNA genome
  • 2 surface antigens - haemagglutinin + neuraminidase
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2
Q

What type of virus is influenza?

A

Orthomyxoviridae

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3
Q

What do the haemagglutinin (H) surface antigens on influenza virus do?

A

Binds to cells of infected person

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4
Q

What do the neuraminidase (N) surface antigens on influenza virus do?

A

Release virus from the host cell surface

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5
Q

Types of influenza

A

Influenza A,B + C

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6
Q

Who does influenza A effect?

A

Humans
Birds
Swine - pigs

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7
Q

Who does influenza B effect?

A

Only humans

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8
Q

Who does influenza C effect?

A

Humans
Swine - pigs

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9
Q

What is the mildest form of influenza?

A

Influenza C

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10
Q

Clinical manifestations of influenza C

A

Mild disease
No seasonality

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11
Q

Clinical manifestations of influenza B

A

Severe disease
Often in older adults or people at higher risk

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12
Q

Clinical presentation of influenza A

A

Could cause large pandemics
Significant mortality in young persons

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13
Q

Transmission of influenza virus

A

Respiratory
e.g. coughing, sneezing, inhaling

  • small article aerosols in air
  • direct contact with larger particles or droplets
  • indirect contact of viral particles on surfaces
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14
Q

What are barriers to entry via respiratory route

A
  • Respiratory epithelial cells - thick glycocalyx + tracheobronchial mucus
  • Ciliated respiratory epithelial cells - sweep mucus up respiratory tract
  • Macrophages, natural killer cells, secretory IgA - immunological defences in lungs
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15
Q

How does the influenza virus enter cells?

A

1- H antigen allows virus to bind to NANA residues
2- invagination of membrane
3- formation of endocytosis vesicle
4- release of virion (virus particle) into cytoplasm

Entry via receptor mediated endocytosis

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16
Q

Symptoms of influenza

A

Fever
Headache
Dry cough
Nasal congestion
Muscle ache

Nausea + vomiting - in children

17
Q

Complications of influenza

A

Meningitis
Pneumonia
Sinusitis/bronchitis/pharyngitis
Maternal complications
Croup - more common in children
Otitis media - more common in children

18
Q

Incubation period of influenza virus

A

1-5 days

19
Q

Who do most serious complications from influenza occur in?

A

Children under 6 months
> 65 years old
Underlying health conditions
Pregnant women (+ 2 weeks post partum)
Morbid obesity BMI>40

20
Q

Recovery time for influenza

A

2-7 days

21
Q

Treatments for influenza

A
  • antivirals rimantadine + amantadine - inhibit viral uncoating after uptake
  • neuraminidase inhibitors oseltamivir + zanamivir - inhibit val release from infected cell + cause aggression of viral particles influenza A+B
22
Q

What drugs can be used to treat influenza?

A

rimantadine + amantadine
oseltamivir + zanamivir

23
Q

Outline the vaccinations for influenza as prevention methods

A

Vaccinations

  • formalin-inactivated (not live) vaccine (quadrivalent/trivalent) by injection
  • live attenuated cold adapted vaccine (quadrivalent) by nasal spray (for children)
24
Q

What vaccine is given to children for influenza?

A

Live, attenuated, cold adapted vaccine (quadrivalent) by nasal spray

25
Q

What vaccine is given to adults for influenza?

A

Formalin-inactivated vaccine (quadrivalent/trivalent) by infection
Not live

26
Q

Why are there different strains of influenza virus?

A

Viral RNA polymerase have a high error rate

27
Q

What is antigenic drift?

A

Minor changes (natural mutations) in the gene of flu viruses that occur gradually over time&raquo_space; seasonal epidemics

28
Q

What is antigenic drift due to?

A

Random mutations in viral RNA
Single or few amino acid substitutions in H + N proteins

29
Q

What is antigenic shift?

A

Minor changes in genes of flu viruses that occur suddenly when two or more different strains combine
Result in a new subtype&raquo_space; casues widespread epidemics/pandemics

30
Q

What is antigenic shift due to?

A

Reassortment of different RNA segments from each species in a new capsid&raquo_space; new subtype made

31
Q

Consequences of antigenic shift

A

New subtype of virus made
Can cause epidemic/pandemic as immune system will have no defence against new strain

32
Q

Where does a secondary infection after influenza commonly occur?

A

In lungs

33
Q

What is influenza?

A

A acute viral infection of respiratory tract

34
Q

Influenza A

A

Effects animals + humans
Undergoes antigenic drift + shift
Responsible for pandemics

35
Q

Influenza B

A

Only effects humans
Undergoes antigenic drift
Mainly affects older adults

36
Q

Influenza C

A

Affects humans + pigs
Undergoes antigenic drift
Produces mild disease

37
Q

Diagnosis of influenza

A

From symptoms and clinical assessment
There are rapid antigen tests + PCR

38
Q

What is a cold adapted vaccine?

A

Virus can grow in nose + throat but not in lower respiratory tract where temp is higher

Infection Diseases (22 decks)

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