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infection > Influenza > Flashcards

Influenza Flashcards

1
Q

In what months does seasonal influenza occur?

A

Seasonal influenza occurs during winter months:

  • Dec to Feb in Northern hemisphere
  • Jun to Aug in Southern hemisphere
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2
Q

Why do epidemics of influenza occur every roughly 11 years?

A

Epidemics occur every 11 years which is thought to be linked to sunspot activity that causing antigenic shifts in viral RNA (mutation)

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3
Q

What kind of virus is influenza?

A

Is an RNA virus with 8 segment genome:

  • Orthomyxoviridae family
  • Three main groups
    • Influenza A
      • Mammals and birds
    • Influenza B
      • Only humans
    • Influenza C
      • Only humans
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4
Q

What are the 3 main groups of influenza and what animals do they infect?

A
  • Influenza A
    • Mammals and birds
  • Influenza B
    • Only humans
  • Influenza C
    • Only humans
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5
Q

From what family of viruses is influenza from?

A
  • Orthomyxoviridae family
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6
Q

What are the surface proteins of influenza?

A
  • 18 different H antigens (H1-3 in humans)
    • Haemagglutinin (H)
      • Facilitates viral attachment and entry to host cell
  • 11 different N antigens
    • Neuraminidase (N)
      • Enables new virion to be released from host cell
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7
Q

What is the function of haemagglutinin?

A
  • Facilitates viral attachment and entry to host cell
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8
Q

What is the function of neuraminidase?

A
  • Enables new virion to be released from host cell
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9
Q

What is antigenic drift?

A
  • Is mechanism of genetic variation within virus
  • Occurs continuously over time, small on-going point mutations in genes coding for antibody binding sites
  • May change the antigenic properties and eventually immune system will not combat virus well
  • Causes worse than normal epidemics and vaccine mismatch
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10
Q

What are consequences of antigenic drift?

A
  • Causes worse than normal epidemics and vaccine mismatch
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11
Q

What is antigenic shift?

A
  • Is abrupt major changes in virus resulting in new H/N combinations
  • Enables flu strain to jump from one animal species to another
  • Process by which two or more different strains of virus combine to form new subtype, creating new H/N combincations (reassortment)
  • With new antigenic properties can lead to pandemics due to population being unprotected
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12
Q

What are consequences of antigenic shift?

A
  • With new antigenic properties can lead to pandemics due to population being unprotected
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13
Q

Compare and contrast seasonal flu and pandemic flu in terms of when it occurs, incidence and severity?

A
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14
Q

What are pandemic requirements?

A
  • Human pathogenicity
  • ‘New’ virus (antigenic shift), creating susceptible population
  • Efficient person-person transmission
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15
Q

How can you describe the incidence of pandemics over the year?

A

Incidence of pandemics is still a wave due to being worse in winter

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16
Q

What is avian flu?

A

Refers to disease caused by infection with avian (bird) influenza

Only a few strains affect humans, spreads through direct contact with infected birds that are either dead or alive

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17
Q

What is the clinical presentation of influenza?

A
  • Abrupt fever up to 41oC which lasts 3 days (range 1-5 days)
  • Plus 2 or more of
    • Cough, myalgia, headache, malaise
  • Predominance of systemic symptoms
  • Less common symptoms
    • Nausea, vomiting, diarrhoea
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18
Q

What is the WHO definition of an influenza like illness (ILI)?

A
  • Fever and
  • Cough
  • Onset within last 10 days
  • If requires hospitalisation is defined as severe acute respiratory infection (SARI)
19
Q

What does ILI stand for?

A

Influenza like illness

20
Q

What does SARI stand for?

A

Severe acute respiratory infection

21
Q

What are the ways influenza can be transmitted?

A
  • Airborne
    • Person to person by large droplets (>5 microns)
  • Contact
    • Direct (person to person)
    • Indirect (person to fomite to person)
22
Q

What is virus shedding?

A
  • Refers to expulsion and release of virus following successful reproduction during host-cell infection
23
Q

When does virus shedding of influenza occur?

A

Virus shedding occurs in first 4 days of illness (range is 1 to 7 days):

  • Refers to expulsion and release of virus following successful reproduction during host-cell infection
  • Longer in young children and immunocompromised
24
Q

What is the virus survival time of influenza on non-porous and porous surfaces?

A
  • 24-48 hours on non-porous surfaces
  • 8-12 hours on porous surface such as tissue
25
Q

What are some risk factors (high risk groups) for complicated influenza?

A
  • Neurological, hepatic, renal, pulmonary and chronic cardiac disease
  • Diabetes mellitus
  • Severe immunosuppression
  • Age over 65 years
  • Pregnancy (including up to two weeks post-partum)
  • Children under 6 months of age
  • Morbid obesity (BMI ≥40)
26
Q

What are some complications of influenza?

A
  • Common
    • Acute bronchitis
    • Secondary bacterial pneumonia
  • Less common
    • Primary viral pneumonia
    • Myocarditis/pericarditis
    • Transverse myelitis/Guillain-Barre
    • Myositis and myoglobinuria
27
Q

Severity assessment of secondary bacterial pneumonia from influenza uses what score to asses severity?

A

CURB65 score

28
Q

Describe the CURB65 score?

A
  • Confusion
  • Urea >7mmol/l
  • Respiratory rate >30mm
  • Blood Pressure (diastolic <60 or systolic <90)
  • >65 years of age

Risk of death in next 30 days increases as CURB65 score increases

29
Q

When should patients with influenza get an urgent chest x-ray?

A

Patients with “flu symptoms and fever for >4 days” should have an urgent chest x-ray

30
Q

How is influenza diagnosed?

A
  • Viral nose and throat swabs (molecular detection/PCR flocked swabs)
31
Q

What investigations are done for influenza?

A
  • Chest x-ray
    • Pneumonitis/pneumonia/ARDSS
  • Blood culture
  • Pulse oximetry
  • Respiratory rate
  • U&Es, FBC, CRP
32
Q

When should antivrial therapy be used for influenza?

A

Use ASAP and within 48 hours of symptoms onset

33
Q

What are the different kinds of antiviral therapy for influenza?

A
  • Oseltamivir
    • Oral administration
    • Dose if over 13 years is 75mg every 12 hours for 5 days
    • Adverse effects
      • Common – Nausea, vomiting, abdominal pain, diarrhoea
      • Less Common – Headache, hallucinations, insomnia and rash
  • Zanamivir
    • Inhaled or IV administration
    • Dose if over 12 years is 10mg inhaled daily for up to 10 days
    • Adverse effects
      • Rare - occasional bronchospasms
34
Q

Describe the lines of treatment for influenza?

A

1st line - oseltamivir

2nd line - zanamivir

35
Q

Other than oseltamivir and zanamivir, what are some other antiviral therapies?

A
  • Peramivir
    • Neuroaminidase inhibitor
    • IV infusion for uncomplicated influenza
  • Favipiravir
    • Viral RNA polymerase inhibitor
    • Oral
  • Baloxavir marboxil
    • Endonuclease inhibitor
    • One single dose
36
Q

What is the pregnancy guidelines for treatment of influenza?

A
  • Antivirals are recommended
  • Oseltamivir remains first line option
37
Q

What is the breastfeeding guidance for influenza treatment?

A
  • Current guidance is oral oseltamivir
38
Q

When does somone with influenza become non-infectious?

A

Immunocompetent adult:

  • 24 hours after last flu symptoms (fever and cough)
  • Or when anti-viral therapy completed
  • Whichever is longer

Immunocompromised adults and young children:

  • Consider each case separately
39
Q

What protection against influenza can healthcare staff use?

A
  • Surgical face mask
  • Plastic apron
  • Gloves
  • Wash hands after any examination
40
Q

What kind of administration is the seasonal influenza vaccine?

A

Intramuscular injection

41
Q

How is the season influenza vaccine prepared?

A
  • Prepared from viruses considered to most likely be circulating in forthcoming Winter
  • Grown in chick embryos
  • Chemically inactivated and purified, trivalent vaccines
    • Containing 2 type A and 1 type B subtype viruses

So cannot be used with egg allergy

42
Q

How many types of influenza does the seasonal vaccine contain?

A
  • Containing 2 type A and 1 type B subtype viruses
43
Q

Why should healthcare workers be vaccinated against influenza?

A
  • To protect themselves and families
  • Reduce the risk to at risk patients
  • Reduce absence from work during influenza surge activity

infection (15 decks)

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