Influenza Flashcards

1
Q

What causes influenza?

A

The influenza virus, part of the orthomyxoviridae family.

Comes in groups A, B & C
IfA - mammals and birds
IfB/C - Only affect humans

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2
Q

Most influenza is seasonal, occurring during the winter months, why do we think that is?

A

Several theories:

  • Vit D prevents viral infections
  • Solar radiation mutates viral RNA creating new strains
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3
Q

Describe the structure of the influenza virus?

A

Two major Surface Antigens:

  • Neuraminidase (N) enables new virus release from host cell
  • Haemaglutinin (H) enables viral entry to host cell
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4
Q

How are new influenza strains produced?

A

By antigenic drift - small changes to the H/N layout over time hence why we get epidemics and need new vaccines every year

By Antigenic Shift - Abrupt major change to the H/N layout due to combination of 2 strains and reassortment of the viral gene segments –> Creating flu strains that jump species causing pandemics

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5
Q

Give an example of influenza antigenic shift?

A

Combination of Human/Avian influenza to form the swine flu pandemic.

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6
Q

How is influenza transmitted?

A

1) Droplet
2) Direct person-person contact
3) Indirect person-fomite-person contact (the virus can survive 48 hrs on non-porous surfaces)

Avian flu is also transmitted by contact with infected birds (dead or alive)

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7
Q

Risk factors for a flu infection?

A
  • Existing disease (neuro/hepatic/renal/cardiac/pulm)
  • Immunocompromise incl. DM
  • > 65 yrs or <6months
  • Pregnancy- including 2 weeks after birth
  • Morbid Obesity
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8
Q

How does influenza present?

A
Abrupt high fever lasting 3 days 
Plus 2 or more of:
- Cough
- Sore throat or rhinorrhoea
- Myalgia
- Headache
- Malaise

Less often they may get N&V + Diarrhoea

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9
Q

How do you test someone for Influenza infection?

A

1) Viral swabs for PCR & molecular detection
2) CXR in case of pneumonia
3) Blood Cultures
4) Pulse Oximetry & Resp rate
5) U&Es, FBC & CRP

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10
Q

A major complication of Influenza is Secondary Bacterial Pneumonia, what do we do if we suspect it?

A

CURB65 Score:

  • Confusion
  • Urea >7mmol/l
  • Resp Rate >30
  • BP <60D OR <90S
  • > 65yrs`
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11
Q

How do we treat Influenza?

A

If its complicated or at risk e.g. immunosuppressed give them antivirals within 48hrs:
Specifically Neuraminidase inhibitors i.e:
- Oral Oseltamavir (5 days)
- Inhaled Zanamivir (10 days)
- Peramivir

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12
Q

What defines complicated Influenza?

A
  • Hospitilisation
  • Affects the LRT
  • Affects the CNS
  • Exacerbates an underlying condition
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13
Q

How do you treat pregnant influenza?

A

Oral Oseltamavir

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14
Q

At what point is influenza considered non-infectious?

A
  • 24 hrs after the last symptoms
  • When anti-viral therapy is completed

Whichever’s first

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15
Q

How do we prevent the spread of influenza within hospital?

A

Staff should use:

  • Face masks
  • Plastic Apron
  • Gloves
  • Hand Hygiene

If doing an aerosolising procedure e.g. nebuliser or NIV then use a Gown, Eye protection and a FPP3 respiratory mask.

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16
Q

How is the flu vaccine produced?

A

It changes every year based on the 3 most common strains that year, (2 type A & 1 type B).
Its contraindicated in egg allergies as its grown in chick embryos.

17
Q

What are the major complications of Influenza?

A
Respiratory
-Acute bronchitis
-SEcondary Bacterial 
-Pneumonia 
Cardiac 
-Myocarditis
-Pericarditis 

CNS

  • Guillain-Barre
  • Transverse myelitis
  • Encephalitis
  • Myositis and myoglobinuria
18
Q

Describe the differences between seasonal flu and pandemic flu

A

Seasonal occurs every winter affecting 10% of the pop and is largely non-lifethreatening in the healthy.

Pandemic flu occurs ~3/century affecting >25% of the pop. and is dangerous with frequent complications.

19
Q

What defines a pandemic?

A

Effect humans
Be new to the pop.
Show efficient human-human transmission

20
Q

What is an influenza like illness?

A

A fever and cough that onsets within the last 10 days.

IF its severe enough to warrant hospitlization its called Severe Acute Respiratory Infection (SARI)

21
Q

viral shedding and viral survival in influenza

A

Virus shedding- release of progeny
• First 4 days
• Longer in children and immunocompromised

Virus Survival
• 24-48 hours on non-porous surfaces
• 8-12 hours on porous surface e.g. tissue