Influenza Flashcards

1
Q

What shift in viral DNA can be caused by mutations due to the sun’s radiation?

A

Antigenic shift

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2
Q

What are features of the influenza virus?
Family
RNA or DNA virus - so mutation is quicker/slower
3 main groups and their respective susceptible groups

A

-From orthomyxoviridae family
-RNA virus
-3 types
>IfA (infects mammals and birds)
>IfB and IfC (infects humans only)

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3
Q

What are 2 surface proteins of the influenza virus?

What are their respective functions

A

> Haemagglutinin (H) - facilitates viral entry to host cell H1-3 in humans

> Neuraminidase (N) - enables new virion to be released from host cell

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4
Q

Discuss antigenic drift?
Define in 2 sentences
Antigenic drift causes… [2]

A
  • Is the mechanism of genetic variation within the virus
  • Small ongoing point mutations in genes coding for antibody binding sites
  • Antigenic properties change = immune system doesn’t combat virus as well
  • Causes vaccine mismatch and normal epidemics
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5
Q

Discuss antigenic shift?
Define in 2 sentences
Pathogenesis in 2 sentences
Causes… [1]

A
  • Abrupt major virus change = new H/N combinations
  • Enables flu strain to jump from one animal species to another
  • 2 or more different viral strains combine to form new subtype
  • Reassortment of virus gene segments
  • Leads to PANDEMICS
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6
Q

What is a well known example of a pandemic that took place?

A

H1N1 virus in 2009/10

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7
Q

How is seasonal flu and pandemic flu different?
Occurrence
Affected population
Complications

A

Seasonal flu

  • occurs every winter
  • affects 10-15%
  • usually unpleasant but not life threatening

Pandemic flu

  • occurs sporadically
  • affects 25%+
  • more serious/complications
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8
Q

What are the requirements for a pandemic to take place? [3]

A

> human pathogenicity
‘new’ virus (antigenic shift)
efficient human-human transmission

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9
Q

Discuss avian influenza:

  • strains
  • transmissions
  • fatality rate
A
  • Many strains but few affect humans (eg H5N1, H7N9)
  • Direct contact with infected birds. Occasionally close human-human contact. Not through properly cooked foods
  • Fatality rate high (eg 60% H5N1)
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10
Q
What are clinical features of Influenza?
Incubation period
Fever characteristics + 2 more of 4 other features
Predominance of x in presenting picture
Less common symptoms 3
A

> Around 2-4d incubation
Abrupt fever lasting around 3d maybe assoc w chills
2 more of: cough (sore throat, rhinorrhoea), myalgia, headache, malaise
Predominance of systemic symptoms
Less commonly: nausea, vomiting, diarrhoea

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11
Q

WHO definition of influenza like illness? [3]

A
  • Fever (>38 degrees) and
  • Cough
  • Onset in last 10d
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12
Q

What is the transmission of Influenza virus? [2]

A

> Airborne: person-person by large droplets (>5 microns)

>Contact: direct (person-person) or indirect (person-fomite-person)

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13
Q

How long does it take for influenza virus to shed?

A

First 4d of illness. Longer in children and immunocompromised

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14
Q

How long does virus survive on surfaces?

Porous vs non-porous

A
  • 24-48h on non-porous surfaces

- 8-12h on porous surfaces (eg tissue)

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15
Q

What are high risk groups for complicated influenza? [5]

A
  • Neurological, hepatic, renal, pulmonary, chronic cardiac disease
  • DM, morbid obesity BMI >40
  • Severe immunosuppression
  • > 65y, <6m
  • Pregnancy (third trim)
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16
Q

What are common respiratory complications of influenza virus? [2]
What 3 organisms can present as part of complications?

A
  • Acute bronchitis
  • Secondary bacterial pneumonia (4-5d after flu start)

Microbiology

  • S. pneumoniae
  • S. aureus
  • H. influenzae
17
Q

What is an uncommon respiratory complication of influenza virus?
Which type of influenza does it commonly appear?
Presentation [2 features]
Mortality rate

A

Primary viral pneumonia

  • common in avian influenza cases
  • rapid respiratory failure in 48h
  • mortality >40% in 7d
18
Q

What is an uncommon cardiac complication of influenza virus?

A

Myocarditis/pericarditis

19
Q

What is an uncommon neurological/CNS complication of influenza virus? [3]

A
  • Transverse myelitis/GBS
  • Myositis and myoglobinuria
  • Reye’s syndrome (children)
20
Q

How is a diagnosis made in Influenza virus? [7]

A
>Viral nose and throat swabs/VTS (pcr)
>CXR (eg pneumonia)
>Blood culture
>Pulse oximetry - SpO2 <92% need ABG and O2
>Resp rate***
>U and E
>FBC, CRP
21
Q

What are the two main antiviral therapy drugs? (2 examples of neuraminidase inhibitors)
ROA
SE

A

> Oseltamivir - oral

  • common side effects: n+v, abd pain, diarrhoea
  • less common side effects: headache, hallucinations, insomnia
  • usually 1st line

> Zanamivir - inhaled/nebulised/IV
-rare side effect - bronchospasm

22
Q

What are other antiviral therapy drugs? [2]

A
  • Peramivir (neuraminidase inhibitor)

- Favipiravir (viral RNA polymerase inhibitor)

23
Q

What is the guidance for antiviral therapy when a woman is pregnant/breastfeeding? [2]

A

> As normal for pregnancy

>Oral oseltamivir for breastfeeding

24
Q

When do immunocompetent adult patients become non-infectious?

A

Immunocompetent:

-24h after last flu symptoms or when antiviral therapy completed

25
Q

What is used for protection when dealing with patients with suspected/proven flu? [4]

A

> Surgical face mask
Plastic apron
Gloves
Washing hands afterwards

26
Q

Why is the yearly flu vaccine contraindicated in those with egg allergy?

A

Grown in allantoic cavity of chick embryos

27
Q

How is the yearly flu vaccine delivered? What is a side effect?

A

> IM injection

>Only adverse effect established is sore arm